Single/multiple comma separated HTTPS URLs or/and single/multiple comma separated Credential IDs to send build notifications to Google Chat rooms.
To use Credential ID as URL identifier configure entire URL as secret in credential. Use id:credential_id as value in URL.
Different Ways to define:
1) https://chat.googleapis.com/v1/spaces/room_id/messages?key=key_id&token=token_id
2) https://chat.googleapis.com/v1/spaces/room_id/messages?key=key_id&token=token_id, https://chat.googleapis.com/v1/spaces/room_id2/messages?key=key_id2&token=token_id2
3) id:credential_id_for_room1
4) id:credential_id_for_room1, id:credential_id_for_room2
5) https://chat.googleapis.com/v1/spaces/room_id/messages?key=key_id&token=token_id, id:credential_id_for_room2