This is a great enhancement as I think that most of the installations have more than one team and users on more than one of them simultaneously.
It's already easier with GitLab SSO but it's still problematic as Mattermost doesn't take into account that two SSOs from GitLab are in fact the same user.
- Will the notification settings be the same in all teams? There will be use cases where users would be mostly active on one team and rather passive observers on others. These users won't like the same notification level on all teams.
- Did you think about the "team amin" role? This one definitely has to be set per team.
- The theme color per team would be a nice to have, the per team notification setting would be more important to me.
- users should only be able to see and message users it they both have permission in at least one common team
- DM have to be finally placed in one team area as there is no "team free" UI or do you intend to make one? If there is only one common team between the users the DM has to be placed there, but what when there are more than one? Which notification settings will be used?