Separate cleanly between public and private APIs

The "private" API here means the API used by our only dynamic view, the upcoming event view. The reason for separating the two is to highlight the fact that the code in api/ is used by other people to connect to our website (or at least in theory could be used to do that), while the code in championship/ can be freely modified by us to add or remove fields.

Conceptually, it also makes more sense that code only used by one championship view lives in championship, while public API code lives under api/. Finally, it also removes the private API views from the API router exposed at unityleague.ch/api.

This commit as a byproduct also deletes an autocomplete view that is not used anywhere, as far as I can tell.