lots of improvements

app/Models/ForumTopic.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+class ForumTopic extends Model
+{
+    protected $fillable = [
+        'thread_id',
+        'user_id',
+        'title',
+        'content',
+        'is_pinned',
+        'last_activity_at',
+    ];
+
+    protected $casts = [
+        'is_pinned' => 'boolean',
+        'last_activity_at' => 'datetime',
+    ];
+
+    /**
+     * Get the thread that owns the topic.
+     */
+    public function thread()
+    {
+        return $this->belongsTo(ForumThread::class, 'thread_id');
+    }
+
+    /**
+     * Get the user that owns the topic.
+     */
+    public function user()
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    /**
+     * Get the posts for the topic.
+     */
+    public function posts()
+    {
+        return $this->hasMany(ForumPost::class, 'topic_id');
+    }
+}