Mapping keys in filter_data are guaranteed to be defined but might be
None for boolean filters. We want to ensure that we actually pass
booleans to generate_program_entries.

This flag allows clients to define what they expect as default behaviour
for setting the ProgramEntry start and end attributes.

If the flag is set steering ensures that ProgramEntry.start never starts
before the requested start and that ProgramEntry.end never ends after
the requested end.

This makes it easy to list entries with specific ids, which comes in
handy when clients want to fetch multiple known objects at once.

This reverts merge request !42

This filter is currently applied programmatically in the dashboard. It
makes much more sense to do this on a database level.

refs dashboard#246

These filters now support datetimes as well as dates and their naming
now reflects what they are querying.

The default values break some valid use cases and there’s no real value
in applying them by default.

refs #189

The filter annotation for ordering by show ownership introduced
a join that caused some results to appear more than once.

The dashboard must be able to sort shows.

In aa7e7f41 filters were renamed
to a camelCase scheme. This is actually wrong, because the filter
names are already transformed to snake_case when the are applied
to the FilterSet.

The nested timeslot routes allowed us to filter the timeslots by show
and schedule. We’ve deprecated nested endpoints with the alpha.2
release, but still need the actual filtering logic.

To be honest I'm not sure this is the right way to do it.

This is mainly so we can start phasing out nested routes.
With nested routes objects were filtered based on route parameters.
Therefore we need something similar in the form of query parameters.

Fixes: #133