nixos/dependency-track: fix nginx config for frontend (#393041)

nixos/modules/services/web-apps/dependency-track.nix

···
       upstreams.dependency-track.servers."localhost:${toString cfg.port}" = { };
       virtualHosts.${cfg.nginx.domain} = {
         locations = {
-          "/".alias = "${cfg.package.frontend}/dist/";
+          "/" = {
+            alias = "${cfg.package.frontend}/dist/";
+            index = "index.html";
+            tryFiles = "$uri $uri/ /index.html";
+            extraConfig = ''
+              location ~ (index\.html)$ {
+                add_header Cache-Control "max-age=0, no-cache, no-store, must-revalidate";
+                add_header Pragma "no-cache";
+                add_header Expires 0;
+              }
+            '';
+          };
           "/api".proxyPass = "http://dependency-track";
-          "= /static/config.json".alias = frontendConfigFile;
+          "= /static/config.json" = {
+            alias = frontendConfigFile;
+            extraConfig = ''
+              add_header Cache-Control "max-age=0, no-cache, no-store, must-revalidate";
+              add_header Pragma "no-cache";
+              add_header Expires 0;
+            '';
+          };
         };
       };
     };

nixos/tests/dependency-track.nix

···
         };
     };
 
-    testScript = ''
-      import json
+    testScript =
+      # python
+      ''
+        import json
+
+        start_all()
 
-      start_all()
+        server.wait_for_unit("dependency-track.service")
+        server.wait_until_succeeds(
+          "journalctl -o cat -u dependency-track.service | grep 'Dependency-Track is ready'"
+        )
+        server.wait_for_open_port(${toString dependencyTrackPort})
 
-      server.wait_for_unit("dependency-track.service")
-      server.wait_until_succeeds(
-        "journalctl -o cat -u dependency-track.service | grep 'Dependency-Track is ready'"
-      )
-      server.wait_for_open_port(${toString dependencyTrackPort})
+        with subtest("version api returns correct version"):
+          version = json.loads(
+            server.succeed("curl http://localhost/api/version")
+          )
+          assert version["version"] == "${pkgs.dependency-track.version}"
 
-      with subtest("version api returns correct version"):
-        version = json.loads(
-          server.succeed("curl http://localhost/api/version")
-        )
-        assert version["version"] == "${pkgs.dependency-track.version}"
-    '';
+        with subtest("nginx serves frontend"):
+          server.succeed("curl http://localhost/ | grep \"<title>Dependency-Track</title>\"")
+      '';
   }
 )