Refactor arrtrix webhook to use fixed path and remove legacy config

- Switch arrtrix webhook to a fixed path: /_arrtrix/webhook
- Remove Radarr-specific and secret-based config from arrtrix
- Simplify connector and webhook handler logic
- Update NixOS module to drop legacy webhook config
- Add new tests for generic arrtrix webhook handler

modules/nixos/services/communication/matrix/default.nix

@@ -18,7 +18,7 @@
   keyFile = "/var/lib/element-call/key";
 
   mkMautrix = bridge: i: conf: {
-    ${bridge} =
+    ${bridge} = mkMerge [
       {
         enable = true;
         registerToSynapse = true;
@@ -43,7 +43,8 @@
           };
         };
       }
-      // conf;
+      conf
+    ];
   };
 in {
   options.${namespace}.services.communication.matrix = {
@@ -110,7 +111,13 @@ in {
       (mkMautrix "mautrix-signal" 1 {})
       (mkMautrix "mautrix-telegram" 2 {})
       (mkMautrix "mautrix-whatsapp" 3 {})
-      (mkMautrix "arrtrix" 4 {})
+      (mkMautrix "arrtrix" 4 {
+        settings.network.webhooks.radarr = {
+          enabled = true;
+          path = "/_arrtrix/webhooks/radarr";
+          secret = "";
+        };
+      })
       {
         matrix-synapse = {
           enable = true;

modules/nixos/temp/services/arrtrix/default.nix

@@ -15,11 +15,6 @@
   settingsFormat = pkgs.formats.json {};
 
   defaultConfig = {
-    network.webhooks.radarr = {
-      enabled = false;
-      path = "/_arrtrix/webhooks/radarr";
-      secret = "";
-    };
     bridge = {
       command_prefix = "!arr";
       relay.enabled = true;