MM-25014 - Default Group Name to null, until AllowGroupReference is set (#14651)

* make Group.Name a pointer to allow null

* fix unit tests

* fix build error

* fix unit test

* ensure Name field not nil

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

app/syncables_test.go

@@ -55,7 +55,7 @@ func TestCreateDefaultMemberships(t *testing.T) {
 	}
 
 	gleeGroup, err := th.App.CreateGroup(&model.Group{
-		Name:        model.NewId(),
+		Name:        model.NewString(model.NewId()),
 		DisplayName: "Glee Club",
 		RemoteId:    model.NewId(),
 		Source:      model.GroupSourceLdap,
@@ -65,7 +65,7 @@ func TestCreateDefaultMemberships(t *testing.T) {
 	}
 
 	scienceGroup, err := th.App.CreateGroup(&model.Group{
-		Name:        model.NewId(),
+		Name:        model.NewString(model.NewId()),
 		DisplayName: "Science Club",
 		RemoteId:    model.NewId(),
 		Source:      model.GroupSourceLdap,