completed story 1.1 with QA tests and fixes

app/Models/Notification.php

@@ -0,0 +1,53 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class Notification extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'user_id',
+        'type',
+        'data',
+        'read_at',
+        'sent_at',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'data' => 'array',
+            'read_at' => 'datetime',
+            'sent_at' => 'datetime',
+        ];
+    }
+
+    /**
+     * Get the user that owns the notification.
+     */
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    /**
+     * Mark the notification as read.
+     */
+    public function markAsRead(): void
+    {
+        $this->update(['read_at' => now()]);
+    }
+
+    /**
+     * Scope to filter unread notifications.
+     */
+    public function scopeUnread($query)
+    {
+        return $query->whereNull('read_at');
+    }
+}