I am attempting to add a message to a G-suite group using the group migration API. The POST command looks like this:
https://www.googleapis.com/upload/groups/v1/groups/groupname@domain.com/archive?uploadType=media&access_token=ya29.Gm03...
Assume that "groupname@domain.com" is valid - I'm substituting the correct value here. The access token value is shortened above, but it should be valid. This was obtained using OAuth and the administrator id for my G-Suite domain. I can use this token successfully for the email API.
I have enabled the "group migration API" in my service account, and in my G-suite account, have enabled the scope "https://www.googleapis.com/auth/apps.groups.migration" for that service account. This scope is requested when I get the authentication token.
The problem? http error 401 (Unauthorized). Prior to getting to this point, I had received other http errors, such as 403 (forbidden) due to errors in scope, or 404 (not found) when I had the wrong group id. so I think I have gotten past that. What other steps do I need to take for proper authorization?