Refactor attachment cropping functionality to support multiple variants

- Introduced AttachmentCrop model to manage crop variants for attachments.
- Updated Attachment model to remove direct crop fields and establish relationships with AttachmentCrop.
- Modified AttachmentService to handle storing and updating multiple crop variants (desktop and mobile).
- Adjusted validation rules to accommodate new crop structure.
- Updated database migration to create attachment_crops table and migrate existing crop data.
- Refactored tests to ensure compatibility with the new cropping structure and validate multiple crop variants.
- Enhanced documentation to reflect changes in attachment handling and cropping capabilities.

app/Domains/Attachable/Models/AttachmentCrop.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Domains\Attachable\Models;
+
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+#[Fillable([
+    'attachment_id',
+    'variant',
+    'crop_horizontal',
+    'crop_vertical',
+    'cropped_attachment_id',
+])]
+class AttachmentCrop extends Model
+{
+    public const DESKTOP = 'desktop';
+
+    public const MOBILE = 'mobile';
+
+    public const VARIANTS = [self::DESKTOP, self::MOBILE];
+
+    protected function casts(): array
+    {
+        return [
+            'attachment_id' => 'integer',
+            'crop_horizontal' => 'array',
+            'crop_vertical' => 'array',
+            'cropped_attachment_id' => 'integer',
+        ];
+    }
+
+    public function attachment(): BelongsTo
+    {
+        return $this->belongsTo(Attachment::class);
+    }
+
+    public function croppedAttachment(): BelongsTo
+    {
+        return $this->belongsTo(Attachment::class, 'cropped_attachment_id');
+    }
+}