source: app/Models/Manager.php@ dfae77e

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\Relations\HasMany;

class Manager extends User
{
    use HasFactory;

    protected $table = 'managers';

    protected $primaryKey = 'user_id';

    public $incrementing = false;

    public $timestamps = false;

    protected $fillable = [
        'user_id'
    ];

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

    public function artists(): HasMany
    {
        return $this->hasMany(Artist::class, 'manager_id');
    }

}