dblink now has its own validator function dblink_fdw_validator(), which is
better than the core function postgresql_fdw_validator() because it gets
the list of legal options from libpq instead of having a hard-wired list.
Make the dblink extension module provide a standard foreign data wrapper
dblink_fdw that encapsulates use of this validator, and recommend use of
that wrapper instead of making up wrappers on the fly.
Unfortunately, because ad-hoc wrappers *were* recommended practice
previously, it's not clear when we can get rid of postgresql_fdw_validator
without causing upgrade problems. But this is a step in the right
direction.
Shigeru Hanada, reviewed by KaiGai Kohei
This isn't fully tested as yet, in particular I'm not sure that the
"foo--unpackaged--1.0.sql" scripts are OK. But it's time to get some
buildfarm cycles on it.
sepgsql is not converted to an extension, mainly because it seems to
require a very nonstandard installation process.
Dimitri Fontaine and Tom Lane
