Increase minSdk to 26 (Android 8 / Oreo) (#4177)

<!--
Note: This checklist is a reminder of our shared engineering
expectations.
The items in Bold are required
If your PR involves UI changes:
1. Upload screenshots or screencasts that illustrate the changes before
/ after
2. Add them under the UI changes section (feel free to add more columns
if needed)
If your PR does not involve UI changes, you can remove the **UI
changes** section

At a minimum, make sure your changes are tested in API 23 and one of the
more recent API levels available.
-->

Task/Issue URL:
https://app.asana.com/0/488551667048375/1206486003155266/f

### Description
Increases the `minSdk` to API 26 (aka, Android 8.0 / Oreo). Other than
the `minSdk` change, there should be no actual behaviour changes.

This also includes the following changes:

- removes dead code that can no longer run due to OS-version guards
- removes redundant OS-version guards
- removes any now-redundant usages of `@Suppress("NewApi")` that I
spotted


### Steps to test this PR

- [ ] Ensure CI passes
- [ ] Smoke test app, as much as you can 🙏

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/apps/ApplicationInfoExtensions.kt

@@ -34,28 +34,11 @@ private fun parseAppCategory(category: Int): AppCategory {
 }
 
 fun ApplicationInfo.parseAppCategory(): AppCategory {
-    return if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
-        parseAppCategory(category)
-    } else {
-        AppCategory.Undefined
-    }
-}
-
-fun ApplicationInfo.getAppCategoryCompat(): Int {
-    return if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
-        category
-    } else {
-        -1 // inlined value of CATEGORY_UNDEFINED
-    }
+    return parseAppCategory(category)
 }
 
 fun ApplicationInfo.isGame(): Boolean {
-    val category = getAppCategoryCompat()
-    return if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
-        category == ApplicationInfo.CATEGORY_GAME
-    } else {
-        category == 0 // inlined value of CATEGORY_GAME
-    }
+    return category == ApplicationInfo.CATEGORY_GAME
 }
 
 fun ApplicationInfo.isSystemApp(): Boolean {

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/apps/ui/ManageRecentAppsProtectionActivity.kt

@@ -121,7 +121,7 @@ class ManageRecentAppsProtectionActivity :
     private fun bindViews() {
         binding.manageRecentAppsSkeleton.startShimmer()
         binding.alwaysOn.setOnClickListener {
-            this.launchAlwaysOnSystemSettings(appBuildConfig.sdkInt)
+            this.launchAlwaysOnSystemSettings()
         }
         binding.unrestrictedBatteryUsage.setOnClickListener {
             this.launchIgnoreBatteryOptimizationSettings()

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/service/DeviceShieldTileService.kt

@@ -25,7 +25,6 @@ import android.os.Bundle
 import android.service.quicksettings.Tile.STATE_ACTIVE
 import android.service.quicksettings.Tile.STATE_INACTIVE
 import android.service.quicksettings.TileService
-import androidx.annotation.RequiresApi
 import androidx.appcompat.app.AppCompatActivity
 import androidx.lifecycle.lifecycleScope
 import com.duckduckgo.anvil.annotations.InjectWith
@@ -44,7 +43,6 @@ import kotlinx.coroutines.*
 import logcat.logcat
 
 @Suppress("NoHardcodedCoroutineDispatcher")
-@RequiresApi(Build.VERSION_CODES.N)
 // We don't use the DeviceShieldTileService::class as binding key because TileService (Android) class does not
 // exist in all APIs, and so using it DeviceShieldTileService::class as key would compile but immediately crash
 // at startup when Java class loader tries to resolve the TileService::class upon Dagger setup

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/service/DnsChangeCallback.kt

@@ -23,9 +23,7 @@ import android.net.LinkProperties
 import android.net.Network
 import android.net.NetworkCapabilities
 import android.net.NetworkRequest
-import android.os.Build
 import com.duckduckgo.app.di.AppCoroutineScope
-import com.duckduckgo.appbuildconfig.api.AppBuildConfig
 import com.duckduckgo.common.utils.DispatcherProvider
 import com.duckduckgo.mobile.android.vpn.network.util.getActiveNetwork
 import java.net.InetAddress
@@ -37,7 +35,6 @@ import logcat.asLog
 import logcat.logcat
 
 class DnsChangeCallback @Inject constructor(
-    private val appBuildConfig: AppBuildConfig,
     private val context: Context,
     @AppCoroutineScope private val coroutineScope: CoroutineScope,
     private val dispatcherProvider: DispatcherProvider,
@@ -56,7 +53,7 @@ class DnsChangeCallback @Inject constructor(
             // we only care about changes in the active network
             if (activeNetwork != null && activeNetwork != network) return@launch
 
-            if (appBuildConfig.sdkInt >= Build.VERSION_CODES.O && !same(lastDns, dns)) {
+            if (!same(lastDns, dns)) {
                 logcat {
                     """
                     onLinkPropertiesChanged: DNS changed

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/service/TrackerBlockingVpnService.kt

@@ -787,9 +787,6 @@ class TrackerBlockingVpnService : VpnService(), CoroutineScope by MainScope(), V
 
             for (service in manager.getRunningServices(Int.MAX_VALUE)) {
                 if (TrackerBlockingVpnService::class.java.name == service.service.className) {
-                    if (Build.VERSION.SDK_INT == Build.VERSION_CODES.M) {
-                        return service.started
-                    }
                     return true
                 }
             }

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/ui/notification/DeviceShieldAlertNotificationBuilder.kt

@@ -22,12 +22,10 @@ import android.app.NotificationManager.IMPORTANCE_DEFAULT
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Intent
-import android.os.Build
 import android.os.ResultReceiver
 import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
 import androidx.core.app.TaskStackBuilder
-import com.duckduckgo.appbuildconfig.api.AppBuildConfig
 import com.duckduckgo.di.scopes.AppScope
 import com.duckduckgo.mobile.android.vpn.R
 import com.duckduckgo.mobile.android.vpn.ui.notification.DeviceShieldNotificationFactory.DeviceShieldNotification
@@ -41,10 +39,8 @@ import dagger.Provides
 object DeviceShieldAlertNotificationBuilderModule {
 
     @Provides
-    fun providesDeviceShieldAlertNotificationBuilder(
-        appBuildConfig: AppBuildConfig,
-    ): DeviceShieldAlertNotificationBuilder {
-        return AndroidDeviceShieldAlertNotificationBuilder(appBuildConfig)
+    fun providesDeviceShieldAlertNotificationBuilder(): DeviceShieldAlertNotificationBuilder {
+        return AndroidDeviceShieldAlertNotificationBuilder()
     }
 }
 
@@ -63,19 +59,14 @@ interface DeviceShieldAlertNotificationBuilder {
     ): Notification
 }
 
-class AndroidDeviceShieldAlertNotificationBuilder constructor(
-    private val appBuildConfig: AppBuildConfig,
-) : DeviceShieldAlertNotificationBuilder {
+class AndroidDeviceShieldAlertNotificationBuilder : DeviceShieldAlertNotificationBuilder {
 
-    @Suppress("NewApi") // we use appBuildConfig
     private fun registerAlertChannel(context: Context) {
-        if (appBuildConfig.sdkInt >= Build.VERSION_CODES.O) {
-            val notificationManager = NotificationManagerCompat.from(context)
-            if (notificationManager.getNotificationChannel(VPN_ALERTS_CHANNEL_ID) == null) {
-                val channel = NotificationChannel(VPN_ALERTS_CHANNEL_ID, VPN_ALERTS_CHANNEL_NAME, IMPORTANCE_DEFAULT)
-                channel.description = VPN_ALERTS_CHANNEL_DESCRIPTION
-                notificationManager.createNotificationChannel(channel)
-            }
+        val notificationManager = NotificationManagerCompat.from(context)
+        if (notificationManager.getNotificationChannel(VPN_ALERTS_CHANNEL_ID) == null) {
+            val channel = NotificationChannel(VPN_ALERTS_CHANNEL_ID, VPN_ALERTS_CHANNEL_NAME, IMPORTANCE_DEFAULT)
+            channel.description = VPN_ALERTS_CHANNEL_DESCRIPTION
+            notificationManager.createNotificationChannel(channel)
         }
     }
 

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/ui/notification/VpnEnabledNotificationBuilder.kt

@@ -41,22 +41,20 @@ class VpnEnabledNotificationBuilder {
         private const val VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_DESCRIPTION = "Ongoing state of App Tracking Protection"
 
         private fun registerOngoingNotificationChannel(context: Context) {
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-                val channel =
-                    NotificationChannel(
-                        VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_ID,
-                        VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_NAME,
-                        IMPORTANCE_LOW,
-                    )
-                channel.setShowBadge(false)
-                channel.description = VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_DESCRIPTION
-                val notificationManager = NotificationManagerCompat.from(context)
-                notificationManager.createNotificationChannel(channel)
-                /**
-                 * We needed to create a new channel to fix: https://app.asana.com/0/488551667048375/1206484244032061/f
-                 */
-                notificationManager.deleteNotificationChannel("com.duckduckgo.mobile.android.vpn.notification.ongoing")
-            }
+            val channel =
+                NotificationChannel(
+                    VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_ID,
+                    VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_NAME,
+                    IMPORTANCE_LOW,
+                )
+            channel.setShowBadge(false)
+            channel.description = VPN_FOREGROUND_SERVICE_NOTIFICATION_CHANNEL_DESCRIPTION
+            val notificationManager = NotificationManagerCompat.from(context)
+            notificationManager.createNotificationChannel(channel)
+            /**
+             * We needed to create a new channel to fix: https://app.asana.com/0/488551667048375/1206484244032061/f
+             */
+            notificationManager.deleteNotificationChannel("com.duckduckgo.mobile.android.vpn.notification.ongoing")
         }
 
         fun buildVpnEnabledNotification(

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/ui/notification/VpnReminderNotificationBuilder.kt

@@ -20,7 +20,6 @@ import android.app.Notification
 import android.app.NotificationChannel
 import android.app.NotificationManager.IMPORTANCE_DEFAULT
 import android.content.Context
-import android.os.Build
 import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
 import com.duckduckgo.di.scopes.AppScope
@@ -41,17 +40,15 @@ class RealVpnReminderNotificationBuilder @Inject constructor(
 ) : VpnReminderNotificationBuilder {
 
     private fun registerAlertChannel(context: Context) {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            val notificationManager = NotificationManagerCompat.from(context)
-            if (notificationManager.getNotificationChannel(AndroidDeviceShieldAlertNotificationBuilder.VPN_ALERTS_CHANNEL_ID) == null) {
-                val channel = NotificationChannel(
-                    VPN_ALERTS_CHANNEL_ID,
-                    VPN_ALERTS_CHANNEL_NAME,
-                    IMPORTANCE_DEFAULT,
-                )
-                channel.description = VPN_ALERTS_CHANNEL_DESCRIPTION
-                notificationManager.createNotificationChannel(channel)
-            }
+        val notificationManager = NotificationManagerCompat.from(context)
+        if (notificationManager.getNotificationChannel(AndroidDeviceShieldAlertNotificationBuilder.VPN_ALERTS_CHANNEL_ID) == null) {
+            val channel = NotificationChannel(
+                VPN_ALERTS_CHANNEL_ID,
+                VPN_ALERTS_CHANNEL_NAME,
+                IMPORTANCE_DEFAULT,
+            )
+            channel.description = VPN_ALERTS_CHANNEL_DESCRIPTION
+            notificationManager.createNotificationChannel(channel)
         }
     }
 

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/ui/onboarding/VpnOnboardingActivity.kt

@@ -288,7 +288,7 @@ class VpnOnboardingActivity : DuckDuckGoActivity() {
     fun onVpnConflictDialogGoToSettings() {
         deviceShieldPixels.didChooseToOpenSettingsFromVpnConflictDialog()
 
-        this.launchAlwaysOnSystemSettings(appBuildConfig.sdkInt)
+        this.launchAlwaysOnSystemSettings()
     }
 
     fun onVpnConflictDialogContinue() {

app-tracking-protection/vpn-impl/src/main/java/com/duckduckgo/mobile/android/vpn/ui/tracker_activity/DeviceShieldTrackerActivity.kt

@@ -445,7 +445,7 @@ class DeviceShieldTrackerActivity :
 
     @SuppressLint("InlinedApi")
     private fun openVPNSettings() {
-        this.launchAlwaysOnSystemSettings(appBuildConfig.sdkInt)
+        this.launchAlwaysOnSystemSettings()
     }
 
     fun onVpnConflictDialogContinue() {

app-tracking-protection/vpn-internal/src/main/java/com/duckduckgo/vpn/internal/flipper/PreferencesFlipperPlugin.kt

@@ -18,7 +18,6 @@ package com.duckduckgo.vpn.internal.flipper
 
 import android.content.Context
 import android.content.SharedPreferences
-import android.os.Build
 import android.preference.PreferenceManager
 import androidx.core.content.edit
 import com.duckduckgo.di.scopes.AppScope
@@ -202,11 +201,7 @@ class PreferencesFlipperPlugin @Inject constructor(context: Context) : FlipperPl
         }
 
         private fun getDefaultSharedPreferencesName(context: Context): String {
-            return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-                PreferenceManager.getDefaultSharedPreferencesName(context)
-            } else {
-                context.packageName + "_preferences"
-            }
+            return PreferenceManager.getDefaultSharedPreferencesName(context)
         }
     }
 }