MM-54502 - Update regex to force first character to be alpha (#24675)

Automatic Merge

server/cmd/mmctl/commands/channel_e2e_test.go

@@ -324,7 +324,7 @@ func (s *MmctlE2ETestSuite) TestDeleteChannelsCmd() {
 	s.th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.EnableAPIChannelDeletion = true })
 	defer s.th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.EnableAPIChannelDeletion = *previousConfig })
 
-	user, appErr := s.th.App.CreateUser(s.th.Context, &model.User{Email: s.th.GenerateTestEmail(), Username: model.NewId(), Password: model.NewId()})
+	user, appErr := s.th.App.CreateUser(s.th.Context, &model.User{Email: s.th.GenerateTestEmail(), Username: model.NewUsername(), Password: model.NewId()})
 	s.Require().Nil(appErr)
 
 	team, appErr := s.th.App.CreateTeam(s.th.Context, &model.Team{