Adds the endpoints and store logic to get groups by team and by channel (#10502)

* Adds the endpoints and store logic to get groups by team and by channel

* Remove TODO comments

* Fix unit tests

app/group.go

@@ -164,3 +164,19 @@ func (a *App) ChannelMembersToRemove() ([]*model.ChannelMember, *model.AppError)
 	}
 	return result.Data.([]*model.ChannelMember), nil
 }
+
+func (a *App) GetGroupsByChannel(channelId string, page, perPage int) ([]*model.Group, *model.AppError) {
+	result := <-a.Srv.Store.Group().GetGroupsByChannel(channelId, page, perPage)
+	if result.Err != nil {
+		return nil, result.Err
+	}
+	return result.Data.([]*model.Group), nil
+}
+
+func (a *App) GetGroupsByTeam(teamId string, page, perPage int) ([]*model.Group, *model.AppError) {
+	result := <-a.Srv.Store.Group().GetGroupsByTeam(teamId, page, perPage)
+	if result.Err != nil {
+		return nil, result.Err
+	}
+	return result.Data.([]*model.Group), nil
+}