feat: add premium podcasts to manage subscriptions for premium episodes

app/Config/Autoload.php

app/Config/Filters.php

app/Controllers/BaseController.php

app/Controllers/FeedController.php

app/Controllers/PostController.php

app/Database/Migrations/2020-05-30-101500_add_podcasts.php

app/Database/Migrations/2020-06-05-170000_add_episodes.php

app/Database/Seeds/AuthSeeder.php

app/Entities/Episode.php

app/Entities/Media/BaseMedia.php

app/Entities/Podcast.php

app/Helpers/media_helper.php

app/Helpers/rss_helper.php

app/Helpers/url_helper.php

app/Models/EpisodeModel.php

app/Models/PodcastModel.php

app/Resources/icons/exchange-dollar.svg

app/Resources/icons/lock-unlock.svg

app/Resources/icons/lock.svg

app/Resources/js/app.ts