Mattermost API Authorization via Gitlab SSO

I’m trying to create an application that uses Mattermost API and I’m stuck with Gitlab SSO Authorization as I don’t find any documentation of its API. Is it even possible? Thanks in advance.

Incredibly sorry for the slow response, this was missed.

We have GitLab API endpoints documented here, would that be helpful? https://docs.mattermost.com/deployment/sso-gitlab.html