pg_service.conf file with unknown parameters

Right now, pg_service.conf returns "syntax error" if it encounters a
parameter it doesn't know about.

This seems user-unfriendly, both in the error message (because it really
isn't a syntax error) and in the behaviour itself (because it doesn't work
when sometimes it should).

For example, if I have a service file with gssencmode=disable set, that
service file cannot be used by a psql client linked against libpq from
version 10. Even if the behavior would be identical (since v10 doesn't have
gssencmode).

Is there a particular reason we (1) refuse unknown parameters in the file,
and (2) call it a "syntax error"?

The documentation just says it's "INI format" file -- though in my
experience most other INI file parsers just ignore extra parameters
included..

//Magnus