Rather than dumping extra fields, lets give them a place to live.
Add a list-based extensions field to contact() (and, eventually, everything, but this ticket is only for contact()). Pull the "x-" off of those extra fields, then add them to that list.
It is very common for the contact field to have extra bits, and sometimes only extra bits. Allow for that.
Example: https://api.apis.guru/v2/specs/fec.gov/1.0/openapi.yaml
Rather than dumping extra fields, lets give them a place to live. Add a list-based
extensionsfield tocontact()(and, eventually, everything, but this ticket is only forcontact()). Pull the "x-" off of those extra fields, then add them to that list.