Added a new /api/v1/licenses endpoint for managing License resources via the API.

Added Custom Field Values for people within the API

Adding custom-field-values to licenses type.

New Custom Fields API endpoint

This adds a new API endpoint for Agencies. It can be scoped for agencies that accept cross agency placements from the user's own agency. The intent is for agencies to find the slugs of the agencies where they can create cross-agency placements. These slugs can then be used to create cross agency placements using the placements periods API endpoint. The API serializer also now supplies the agency slug.

Added 2 new fields to the "applications" and "application-summary" objects:

The GET /application_status_changes endpoints now will have an included block containing information about the associated Application object, with the following Application information:

Added a new GET endpoint /custom_key_dates for directly accessing key dates that have been set up by the agency:

Added a compound filter filter[agency_key_date] GET /application_key_dates to allow filtering on custom agency key date information.

Added provider-external-identifier as a field to the GET response payloads for the application_status_changes endpoints