Starting a PostgreSQL server on a dynamic port (parameter port=0)

Hello.

Postgres does not allow starting the server with port=0, which prevents
it from obtaining an arbitrary free port from the kernel.

~$ LANG=C pg_ctl -D data -o "-c port=0" start
2025-07-10 05:27:02.785 GMT [702503] FATAL: 0 is outside the valid
range for parameter "port" (1 .. 65535)

This makes it unreliable to start the server in my tests without the
risk of port conflicts with already running programs, unless resorting
to an unreliable and race-condition-prone procedure of reserving ports
in advance.

Could you please fix this?