refactor: simplify user model

Models shouldn't contain custom logic

app/Models/Subscription.php

@@ -14,6 +14,7 @@
 namespace App\Models;
 
 use App\Traits\Auditable;
+use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 
@@ -48,4 +49,20 @@ class Subscription extends Model
     {
         return $this->belongsTo(Forum::class);
     }
+
+    /**
+     * Only include subscriptions of a forum
+     */
+    public function scopeOfForum($query, $forum_id): Builder
+    {
+        return $query->where('forum_id', '=', $forum_id);
+    }
+
+    /**
+     * Only include subscriptions of a topic
+     */
+    public function scopeOfTopic($query, $topic_id): Builder
+    {
+        return $query->where('topic_id', '=', $topic_id);
+    }
 }