use append_slash_redirect to redirect mailhog path request at root (#84)

mailhog/mailhog/extension.py

@@ -4,6 +4,7 @@
 
 from localstack import config, constants
 from localstack.extensions.api import Extension, http
+from werkzeug.utils import append_slash_redirect
 
 try:
     from localstack.pro.core import config as config_pro
@@ -81,6 +82,11 @@ def on_platform_ready(self):
     def update_gateway_routes(self, router: http.Router[http.RouteHandler]):
         endpoint = http.ProxyHandler(forward_base_url=self.server.url + "/" + self.server.web_path)
 
+        def _redirect_endpoint(request, *args, **kwargs):
+            if not request.path.endswith("/"):
+                return append_slash_redirect(request.environ)
+            return endpoint(request, *args, **kwargs)
+
         # hostname aliases
         router.add(
             "/",
@@ -97,11 +103,10 @@ def update_gateway_routes(self, router: http.Router[http.RouteHandler]):
         # useful, since the webapp needs to be accessed with a trailing slash (localhost:4566/<webpath>/)
         # otherwise the relative urls (like `images/logo.png`) are resolved as
         # `localhost:4566/images/login.png` which looks like an S3 access and will lead to localstack errors.
-        # alas, we disabled this for good reason, so we're stuck with telling the user to add the trailing
-        # slash.
+        # alas, we disabled this for good reason, so we need to catch the request and redirect it if needed
         router.add(
             f"/{self.server.web_path}",
-            endpoint=endpoint,
+            endpoint=_redirect_endpoint,
         )
         router.add(
             f"/{self.server.web_path}/<path:path>",