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_test.go

@@ -197,3 +197,55 @@ func TestDeleteGroupSyncable(t *testing.T) {
 	require.NotNil(t, err)
 	require.Nil(t, gs)
 }
+
+func TestGetGroupsByChannel(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+	group := th.CreateGroup()
+
+	// Create a group channel
+	groupSyncable := &model.GroupSyncable{
+		GroupId:    group.Id,
+		AutoAdd:    false,
+		SyncableId: th.BasicChannel.Id,
+		Type:       model.GroupSyncableTypeChannel,
+	}
+
+	gs, err := th.App.CreateGroupSyncable(groupSyncable)
+	require.Nil(t, err)
+	require.NotNil(t, gs)
+
+	groups, err := th.App.GetGroupsByChannel(th.BasicChannel.Id, 0, 60)
+	require.Nil(t, err)
+	require.ElementsMatch(t, []*model.Group{group}, groups)
+
+	groups, err = th.App.GetGroupsByChannel(model.NewId(), 0, 60)
+	require.Nil(t, err)
+	require.Empty(t, groups)
+}
+
+func TestGetGroupsByTeam(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+	group := th.CreateGroup()
+
+	// Create a group team
+	groupSyncable := &model.GroupSyncable{
+		GroupId:    group.Id,
+		AutoAdd:    false,
+		SyncableId: th.BasicTeam.Id,
+		Type:       model.GroupSyncableTypeTeam,
+	}
+
+	gs, err := th.App.CreateGroupSyncable(groupSyncable)
+	require.Nil(t, err)
+	require.NotNil(t, gs)
+
+	groups, err := th.App.GetGroupsByTeam(th.BasicTeam.Id, 0, 60)
+	require.Nil(t, err)
+	require.ElementsMatch(t, []*model.Group{group}, groups)
+
+	groups, err = th.App.GetGroupsByTeam(model.NewId(), 0, 60)
+	require.Nil(t, err)
+	require.Empty(t, groups)
+}