Ok, if i got this right. I am using the exact same setup as mccoole.
Omnibus gitlab with mattermost, and gitlab as oauth2 provider connected to our ldap server.
You describe the way the zapier uses the api, as an oauth2 app, like described in the docs.
The question is how to authenticate via the api to mattermost,
when there is no "valid credentials" in mattermost itself. Not as a trusted app or something.
Just by using the curl -i -d '{"login_id":"username","password":"mysecret"}' https://example.com/api/v3/users/login
part.
Could we use the gitlab api, to generate a token to access the mattermost api somehow.
Greetings Nev