fix: Correctly adapt starlette BaseUser to A2A User

Author: mikeas1

src/a2a/server/apps/starlette_app.py

@@ -45,8 +45,20 @@
 
 logger = logging.getLogger(__name__)
 
-# Register Starlette User as an implementation of a2a.auth.user.User
-A2AUser.register(BaseUser)
+
+class StarletteUserProxy(A2AUser):
+    """Adapts the Starlette User class to the A2A user representation."""
+
+    def __init__(self, user: BaseUser):
+        self._user = user
+
+    @property
+    def is_authenticated(self):
+        return self._user.is_authenticated
+
+    @property
+    def user_name(self):
+        return self._user.display_name
 
 
 class CallContextBuilder(ABC):
@@ -64,7 +76,7 @@ def build(self, request: Request) -> ServerCallContext:
         user = UnauthenticatedUser()
         state = {}
         with contextlib.suppress(Exception):
-            user = request.user
+            user = StarletteUserProxy(request.user)
             state['auth'] = request.auth
         return ServerCallContext(user=user, state=state)