django-filter new version incompatible with older djangorestframework for /docs endpoint

[oliche]

The documentation of endpoints using coreapi has been deprecated since a while on django-filters and support removed from 25.1.
However we use the automated model self documentation in ONE to propose options.

Here we should update the \docs endpoint to use the recommended drf-spectacular module instead, which may in turn impact how we gather the schemas on the ONE side.

For now I have pinned django-filters to 24.3.

[oliche]

#939