Add some group plugin APIs (#12180)

* Add group store GetByUser

* Add group store GetByName

* Add group plugin APIs

* Minor naming fixes

* Add minimum version comments

app/group.go

@@ -11,6 +11,10 @@ func (a *App) GetGroup(id string) (*model.Group, *model.AppError) {
 	return a.Srv.Store.Group().Get(id)
 }
 
+func (a *App) GetGroupByName(name string) (*model.Group, *model.AppError) {
+	return a.Srv.Store.Group().GetByName(name)
+}
+
 func (a *App) GetGroupByRemoteID(remoteID string, groupSource model.GroupSource) (*model.Group, *model.AppError) {
 	return a.Srv.Store.Group().GetByRemoteID(remoteID, groupSource)
 }
@@ -19,6 +23,10 @@ func (a *App) GetGroupsBySource(groupSource model.GroupSource) ([]*model.Group,
 	return a.Srv.Store.Group().GetAllBySource(groupSource)
 }
 
+func (a *App) GetGroupsByUserId(userId string) ([]*model.Group, *model.AppError) {
+	return a.Srv.Store.Group().GetByUser(userId)
+}
+
 func (a *App) CreateGroup(group *model.Group) (*model.Group, *model.AppError) {
 	return a.Srv.Store.Group().Create(group)
 }