Re: Allow 'sslkey' and 'sslcert' in postgres_fdw user mappings

Re: To Andrew Dunstan 2020-01-09 <20200109103014.GA4192@msg.df7cb.de>
> I believe the options are still used in that case
> for creating connections, even when that means the remote server isn't
> set up for cert auth, which needs password_required=false to succeed.

They are indeed:

stat("/var/lib/postgresql/.postgresql/root.crt", 0x7ffcff3e2bb0) = -1 ENOENT (Datei oder Verzeichnis nicht gefunden)
stat("/foo", 0x7ffcff3e2bb0)            = -1 ENOENT (Datei oder Verzeichnis nicht gefunden)
      ^^^^ sslcert

I'm not sure if that could be exploited in any way, but let's just
forbid it.

Christoph