fix DispatchingJinjaLoader to not use internal methods of parent class

src/capport/api/app_cls.py

@@ -21,11 +21,24 @@ class DispatchingJinjaLoader(quart.templating.DispatchingJinjaLoader):
     def __init__(self, app: MyQuartApp) -> None:
         super().__init__(app)
 
-    def _loaders(self) -> typing.Generator[jinja2.BaseLoader, None, None]:
+    def get_source(
+        self,
+        environment: typing.Any,
+        template: str,
+    ) -> tuple[str, str | None, typing.Callable | None]:
         if self.app.custom_loader:
-            yield self.app.custom_loader
-        for loader in super()._loaders():
-            yield loader
+            try:
+                return self.app.custom_loader.get_source(environment, template)
+            except jinja2.TemplateNotFound:
+                pass
+        return super().get_source(environment, template)
+
+    def list_templates(self) -> list[str]:
+        result = set()
+        if self.app.custom_loader:
+            result.update(self.app.custom_loader.list_templates())
+        result.update(super().list_templates())
+        return list(result)
 
 
 class MyQuartApp(quart_trio.QuartTrio):