refac: pass token_endpoint_auth_method

backend/open_webui/utils/oauth.py

@@ -381,9 +381,20 @@ class OAuthClientManager:
             "name": client_id,
             "client_id": oauth_client_info.client_id,
             "client_secret": oauth_client_info.client_secret,
-            "client_kwargs": (
-                {"scope": oauth_client_info.scope} if oauth_client_info.scope else {}
-            ),
+            "client_kwargs": {
+                **(
+                    {"scope": oauth_client_info.scope}
+                    if oauth_client_info.scope
+                    else {}
+                ),
+                **(
+                    {
+                        "token_endpoint_auth_method": oauth_client_info.token_endpoint_auth_method
+                    }
+                    if oauth_client_info.token_endpoint_auth_method
+                    else {}
+                ),
+            },
             "server_metadata_url": (
                 oauth_client_info.issuer if oauth_client_info.issuer else None
             ),