MDL-84300 core: Support nested templates in routed API

lib/classes/route/api/templates.php

@@ -44,7 +44,7 @@ class templates {
      * @return payload_response
      */
     #[route(
-        path: '/templates/{themename}/{component}/{identifier}',
+        path: '/templates/{themename}/{component}/{identifier:.*}',
         method: ['GET'],
         title: 'Fetch a single template',
         description: 'Fetch a single template for a component in a theme',

lib/tests/route/api/templates_test.php

@@ -64,7 +64,17 @@ final class templates_test extends route_testcase {
                 ['core/modal'],
                 [],
             ],
-            'foo' => [
+            'fetch nested template' => [
+                'boost/core/local/modal/alert',
+                [
+                    'core/local/modal/alert',
+                    'core/modal',
+                ],
+                [
+                    'moodle/ok',
+                ],
+            ],
+            'multiple templates' => [
                 'boost/core/notification',
                 [
                     'core/notification',