castopod/app/Models/UserModel.php

<?php namespace App\Models;

use App\Entities\User;

class UserModel extends \Myth\Auth\Models\UserModel
{
    protected $returnType = User::class;

    public function getPodcastContributors($podcast_id)
    {
        return $this->select('users.*, auth_groups.name as podcast_role')
            ->join('users_podcasts', 'users_podcasts.user_id = users.id')
            ->join('auth_groups', 'auth_groups.id = users_podcasts.group_id')
            ->where('users_podcasts.podcast_id', $podcast_id)
            ->findAll();
    }

    public function getPodcastContributor($user_id, $podcast_id)
    {
        return $this->select('users.*')
            ->join('users_podcasts', 'users_podcasts.user_id = users.id')
            ->where([
                'users.id' => $user_id,
                'podcast_id' => $podcast_id,
            ])
            ->first();
    }
}