Migrate backend to Porto architecture and fix minor bugs

- Fully transitioned the backend to the Porto architectural pattern
- Improved code organization and maintainability
- Fixed minor bugs and inconsistencies

app/Containers/User/Models/AcceptedInvitation.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Containers\User\Models;
+
+use App\Ship\Models\Model;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class AcceptedInvitation extends Model
+{
+    use HasFactory;
+
+    protected $fillable = ['sender_id', 'receiver_id', 'post_limit'];
+
+    public function sender(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'sender_id');
+    }
+
+    public function receiver(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'receiver_id');
+    }
+}