merge auth SP module into main configuration; add enableSso option

`enableSso` is being added to the following SP modules:
* gitea (forgejo)
* nextcloud
* roundcube
* simple-nixos-mailserver

sp-modules/gitea/module.nix

@@ -14,7 +14,7 @@ let
     "gitea-light"
     "gitea-dark"
   ];
-  is-auth-enabled = sp.modules.auth.enable or false;
+  is-auth-enabled = cfg.enableSso;
   oauth-client-id = "forgejo";
   auth-passthru = config.passthru.selfprivacy.auth;
   oauth2-provider-name = auth-passthru.oauth2-provider-name;
@@ -183,6 +183,15 @@ in
         weight = 6;
       };
     };
+    enableSso = (lib.mkOption {
+      default = false;
+      type = lib.types.bool;
+      description = "Enable SSO for Forgejo";
+    }) // {
+      meta = {
+        type = "enable";
+      };
+    };
     debug = lib.mkOption {
       default = false;
       type = lib.types.bool;