Add missing fields to COTF serializer

### Plugin Version

0.4.1

### Proposed functionality

Please add the missing fields to the COTF serializer.

### Use case

This would allow us to use the REST API to duplicate the COT/COTF objects in another NetBox instance, e.g., copy COTs from a DEV instance to a PROD instance.

### External dependencies

N/A

### Missing fields...

required
unique
related_object_filter
