Make link clickable

[sowjanyakch]

Resolve #4672

• General placeholder support for mentions - If the placeholder contains link, replace it with provided name and make it clickable.

Clicking on the testing android2 should redirect to a website.

🚧 TODO

• ...

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[mahibi]

I added one minor change:
to get the current user, please use currentUserProvider whenever possible, instead userManager

[mahibi]

/backport to stable-21.0

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	104	104
Errors	9	9

SpotBugs

Category	Base	New
Bad practice	6	6
Correctness	222	222
Dodgy code	71	71
Internationalization	3	3
Malicious code vulnerability	3	3
Performance	4	4
Security	1	1
Total	310	310

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/4729-talk.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud Talk app.