ext/pgsql: Removed pg_service(), unavailable with any released libpq

[KentarouTakeda]

PQservice() never shipped in a released libpq; it was dropped during the PostgreSQL 18 beta.

See also php/doc-en#5873

[devnexen]

Hi @KentarouTakeda good thinking ; what I would do however if I were you is to "reimplement" on master using the information from the connection itself instead wdyt ?

[KentarouTakeda]

@devnexen
On master, I'd probably add pg_conninfo() instead. pg_service() would use PQconninfo() anyway, and would need a libpq version check since the service is only reported from libpq 18. Exposing PQconninfo() directly avoids that and gives more than just the service name. It's also a thin libpq wrapper, like much of ext/pgsql.

Still, restoring the function from 8.5 makes sense too, and it avoids dealing with the password.

[devnexen]

@adoy @DanielEScherzer @edorian what do you think if we remove this for the next 8.5 release ?