refactor(auth): change contributor's role logic to have it included in the users_podcasts table

- update myth-auth and codeigniter to latest develop changes
- improve permission check: remove all
dynamic permissions per podcast and overwrite myth-auth services and permission filter
- remove
unnecessary code because of myth-auth upgrade
- refactor some controller code for better clarity
-
add remaining seeders in docs

closes #19, #20

app/Models/UserModel.php

@@ -0,0 +1,28 @@
+<?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();
+    }
+}