Moving slash-commands out of app package (#14979)

* Moving slash-commands out of app package

* Fixing golint checks

* Fixing golangci-lint

* Fixing golangci-lint errors

app/helper_test.go

@@ -334,29 +334,6 @@ func (me *TestHelper) createChannel(team *model.Team, channelType string) *model
 	return channel
 }
 
-func (me *TestHelper) createChannelWithAnotherUser(team *model.Team, channelType, userId string) *model.Channel {
-	id := model.NewId()
-
-	channel := &model.Channel{
-		DisplayName: "dn_" + id,
-		Name:        "name_" + id,
-		Type:        channelType,
-		TeamId:      team.Id,
-		CreatorId:   userId,
-	}
-
-	utils.DisableDebugLogForTest()
-	var err *model.AppError
-	if channel, err = me.App.CreateChannel(channel, true); err != nil {
-		mlog.Error(err.Error())
-
-		time.Sleep(time.Second)
-		panic(err)
-	}
-	utils.EnableDebugLogForTest()
-	return channel
-}
-
 func (me *TestHelper) CreateDmChannel(user *model.User) *model.Channel {
 	utils.DisableDebugLogForTest()
 	var err *model.AppError