Is your feature request related to a problem? Please describe.
Trying to set unix:/var/run/whatever.sock in the hostname field of an nginx upstream results in "please specify a valid address (IPv4/IPv6) or hostname" for the hostname and "Field upstream_server.[…].port is required" for the port.

Describe the solution you'd like
When the "hostname" field starts with unix:, allow it and ignore the port.