expose Matrix admin APIs restricted to trusted networks

This is needed to have element-admin work.

config/hosts/matrix/mas.nix

@@ -33,6 +33,17 @@ let
           }];
           proxy_protocol = false;
         }
+        {
+          name = "admin";
+          resources = [{
+            name = "adminapi";
+          }];
+          binds = [{
+            host = "localhost";
+            port = 8082;
+          }];
+          proxy_protocol = false;
+        }
       ];
       trusted_proxies = [
         "127.0.0.1/8"