* Enable dynamic field inclusion for REST API serializers
* Recurse through nested serializer when resolving prefetches
* Remove obsolete calls to prefetch_related() for API views
* Remove support for brief_prefetch_fields viewset attribute
* Rename query parameter
* Fixes#15133: Fix FHRP group representation on assignments endpoint under brief mode (#15134)
* Fixes#15133: Fix FHRP group representation on assignments endpoint under brief mode
* Update API test
* Restore get_queryset() on BriefModeMixin, minus prefetch logic
* get_prefetches_for_serializer() should reference serializer field source if set
* Move L2VPN and L2VPNTermination models from ipam to vpn
* Move L2VPN resources from ipam to vpn
* Extend migration to update content types
* Misc cleanup
- Introduces a new `vpn` app with the following models:
- Tunnel
- TunnelTermination
- IKEProposal
- IKEPolicy
- IPSecProposal
- IPSecPolicy
- IPSecProfile
