Blocking a GitLab user should also deactivate the linked GitLab Mattermost user
Problem to solve
When a user is blocked in GitLab, the linked GitLab Mattermost user is not deactivated.
This was reported by a 100-seat premium customer who had the following comments:
We are running gitlab version 12.7.6-ee with application Gitlab Mattermost which version is reported as being 5.17.3 (DB schema 5.17.0). When we block a user in Gitlab we expect that the user in Mattermost would also be blocked/deactivated (users authenticate through Gitlab). However this is not the case. Now I'm assuming they can't log in, but if they have notification set to email they will receive those. This is a problem for us with external contractors who have their own email address in use. Expected behavior would be that if a user gets blocked in Gitlab it will also disable/deactivate the user in Mattermost.