Add HTTP Headers API integration for mapping

docs/openapi.yaml

setup.py

src/netbox_rps_plugin/__init__.py

src/netbox_rps_plugin/api/serializers.py

src/netbox_rps_plugin/api/urls.py

src/netbox_rps_plugin/api/views.py

src/netbox_rps_plugin/migrations/0002_http_header.py

src/netbox_rps_plugin/models.py