Fix Azure authentication (#1117)

The callback path for authentication in Azure AD, and possibly others, was
unintentionally broken in 8ecd415 by modifying the user-facing path.

This commit reverts one line of that change to restore it to its previous
state.

backend/chainlit/server.py

@@ -332,7 +332,7 @@ def get_user_facing_url(url: URL):
     if config_url.path.endswith("/"):
         config_url = config_url.replace(path=config_url.path[:-1])
 
-    return config_url.__str__()
+    return config_url.__str__() + url.path
 
 
 @router.get("/auth/config")