fix(auth): guard required redirect_uris for pyright and coverage

Author: KirtiRamchandani

src/mcp/server/auth/handlers/register.py

@@ -91,6 +91,15 @@ async def handle(self, request: Request) -> Response:
                 status_code=400,
             )
 
+        if not client_metadata.redirect_uris:
+            return PydanticJSONResponse(
+                content=RegistrationErrorResponse(
+                    error="invalid_client_metadata",
+                    error_description="redirect_uris is required",
+                ),
+                status_code=400,
+            )
+
         for redirect_uri in client_metadata.redirect_uris:
             try:
                 validate_registered_redirect_uri(redirect_uri)