Auth Problems with Google Business Messages

Questions
1

Hi, I’m having trouble getting to authenticate with one of Google API (Business messaging API, this one is not controlled via regular oauth2 flow but rather some custom library GitHub - google/oauth2l: oauth2l ("oauth tool") is a simple CLI for interacting with Google API authentication. · GitHub).
do you guys have any experience on this and can share details on how has you configured this on an HTTP Request node within n8n ?

Information on your n8n setup

  • **n8n version: 1.78.1
  • **Database : SQLite
  • **n8n EXECUTIONS_PROCESS setting : Own
  • **Running n8n via : Docker
  • **Operating system: Ubuntu
2

In case it helps, HTTP Request node support this by selecting Google Service Account API as Credential Type.
then just need to add the service account email, private key and add https://www.googleapis.com/auth/rcsbusinessmessaging as oauth2 scope