Implement get shows by filtering slugs

We should expand the get shows endpoint to filter Category, FundingCategory, Language, MusicFocus, Topic and Type by its slug:

We will research about the best option for this.

Either accept the both types of parameter:

GET /api/v1/shows/?category=<int|slug>
GET /api/v1/shows/?funding_category=<int|slug>
GET /api/v1/shows/?language=<int|slug>
GET /api/v1/shows/?music_focus=<int|slug>
GET /api/v1/shows/?topic=<int|slug>
GET /api/v1/shows/?type=<int|slug>

Or, be explicit about the type of the parameter:

GET /api/v1/shows/?category_pk=<int>
GET /api/v1/shows/?category_slug=<slug>
...