cssd-back/app/Models/Message.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\SoftDeletes;

class Message extends Model
{
    use SoftDeletes;

    public $fillable = ['title', 'text', 'status', 'recipient_user_id', 'sender_user_id'];

    public function sender_user(): BelongsTo
    {
        return $this->belongsTo(User::class, 'sender_user_id');
    }

    public function recipient_user(): BelongsTo
    {
        return $this->belongsTo(User::class, 'recipient_user_id');
    }
}