/api/v1/firewall/nat/outbound/mapping `target` field no longer works correctly on pfSense 2.7.1

[jaredhendrickson13]

Describe the bug
pfSense 2.7.1 has changed the internal names that the target API field expands into. This prevents the rules from working as expected or in some cases prevents them from being loaded at all. The only internal fields now are target and target_subnet.

pfSense Version & Package Version:

• pfSense Version: pfSense 2.7.1 and pfSense 23.09
• Package Version: v1.6.5

Affected Endpoints:

• URL: /api/v1/firewall/nat/outbound/mapping