New-OMIS/Modules/Employee/app/Models/Employee.php

<?php

namespace Modules\Employee\Models;

use App\Models\User;
use Illuminate\Database\Eloquent\Model;

class Employee extends Model
{
    protected $table = 'tbl_employees';
    protected $primaryKey = 'id';
    protected $guarded = [];
    protected $appends = ['full_name'];

    protected function getFullNameAttribute()
    {
        return $this->first_name . ' ' . $this->middle_name . ' ' . $this->last_name;
    }

    public function user()
    {
        return $this->belongsTo(User::class, 'users_id');
    }
}