ChannelStore migration Part 2 (#15405)

* Migration completed

* Several corrections in tests

* Fix imports

* Fix some errors after testing

* Trigger CI

* Fix tests

* Suggestions

* Suggestions

* Add license

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/team.go

@@ -1194,8 +1194,8 @@ func (a *App) LeaveTeam(team *model.Team, user *model.User, requestorId string)
 	for _, channel := range *channelList {
 		if !channel.IsGroupOrDirect() {
 			a.invalidateCacheForChannelMembers(channel.Id)
-			if err = a.Srv().Store.Channel().RemoveMember(channel.Id, user.Id); err != nil {
-				return err
+			if nErr = a.Srv().Store.Channel().RemoveMember(channel.Id, user.Id); nErr != nil {
+				return model.NewAppError("LeaveTeam", "app.channel.remove_member.app_error", nil, nErr.Error(), http.StatusInternalServerError)
 			}
 		}
 	}