added media, mutation events, agent instructions

app/Models/Media.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+
+class Media extends Model {
+    use HasFactory;
+
+    protected $fillable = [
+        'file_path',
+        'file_name',
+        'mime_type',
+    ];
+
+    protected $appends = ['url'];
+
+    public function mediable(): MorphTo {
+        return $this->morphTo();
+    }
+
+    public function getUrlAttribute(): string {
+        return asset('storage/' . $this->file_path);
+    }
+}