Create CI build workflow and optimize ETag module

Add a GitHub Actions CI workflow for building and testing NGINX modules. In the ETag module, skip processing if the request has no upstream to improve efficiency.

.github/FUNDING.yml

@@ -1,6 +1,4 @@
 community_bridge: null
-custom:
-- https://paypal.me/dvershinin
 github: dvershinin
 issuehunt: null
 ko_fi: null

.github/workflows/build.yml

@@ -0,0 +1,46 @@
+name: Test Build
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 2
+      matrix:
+        nginx-branch: [stable, mainline]
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Install build and test dependencies
+        run: |
+          sudo apt-get --yes update
+          sudo apt-get install --yes libpcre3-dev libssl-dev perl cpanminus
+
+      - name: Create NGINX download directory
+        run: mkdir nginx
+
+      - name: Download ${{ matrix.nginx-branch }} NGINX
+        uses: dvershinin/lastversion-action@main
+        with:
+          repository: 'nginx'
+          action: 'unzip'
+          branch: ${{ matrix.nginx-branch }}
+          working_directory: ./nginx
+
+      - name: Configure NGINX to compile with the module statically
+        run: |
+          cd nginx && ./configure --with-debug --add-module=..
+
+      - name: Make NGINX
+        run: |
+          cd nginx && make -j$(nproc)
+
+      - name: Ensure Test::Nginx installed
+        run: |
+          cpanm --notest --local-lib=$HOME/perl5 Test::Nginx
+
+      - name: Test the module
+        run: |
+          PATH=$(pwd)/nginx/objs:$PATH PERL5LIB=$HOME/perl5/lib/perl5 TEST_NGINX_VERBOSE=true prove -v

src/ngx_http_dynamic_etag_module.c

@@ -153,9 +153,13 @@ ngx_http_dynamic_etag_header_filter(ngx_http_request_t *r)
     ngx_http_dynamic_etag_loc_conf_t    *conf;
     ngx_str_t                            enable;
 
-
     conf = ngx_http_get_module_loc_conf(r, ngx_http_dynamic_etag_module);
 
+    // Skip processing if not fetching from upstream (e.g., FastCGI)
+    if (r->upstream == NULL) {
+        return ngx_http_next_header_filter(r);
+    }
+
     if (conf->enable == 0 || r->method & NGX_HTTP_HEAD) {
         return ngx_http_next_header_filter(r);
     } else if (conf->enable == 2) {
@@ -211,6 +215,11 @@ ngx_http_dynamic_etag_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
     unsigned char  digest[16];
     ngx_uint_t     i;
 
+    // If the response is not from the upstream, skip processing
+    if (r->upstream == NULL) {
+        return ngx_http_next_body_filter(r, in);
+    }
+
     ctx = ngx_http_get_module_ctx(r, ngx_http_dynamic_etag_module);
     if (ctx == NULL) {
         return ngx_http_next_body_filter(r, in);