agorakit/agorakit

{
  "require": {
    "php": "^7.3",
    //
    "cviebrock/eloquent-taggable": "^8"
  },
}

use Cviebrock\EloquentTaggable\Taggable;
use Illuminate\Database\Eloquent\Model;

class Group extends Model
{
    use Taggable;
}

class GroupTagController extends Controller
{
    public function edit(Request $request, Group $group, Tag $tag)
    {
        $discussion = new Discussion;
        $discussion->group()->associate($group);

        $tags = collect();

        $discussions = $group->discussions()
            ->with('tags')
            ->get();

        $files = $group->files()
            ->with('tags')
            ->get();

        foreach ($discussions as $discussion) {
            foreach ($discussion->tags as $tag) {
                $tags->push($tag);
            }
        }

        foreach ($files as $file) {
            foreach ($file->tags as $tag) {
                $tags->push($tag);
            }
        }

        $tags = $tags->unique('normalized')->sortBy('normalized');
        //
    }
}