Re: let's make the list of reportable GUCs configurable (was Re: Add%r substitution for psql prompts to show recovery status)

We have steadfastly refused to provide protocol-level tools for things
like "please change my user ID, and don't let anyone change it again
via SQL," and that's a huge problem for things like connection poolers
which can't parse all the SQL flowing through the connection (because
figuring out what it does requires solving the Halting Problem) and
wouldn't want to if they could for performance reasons. I think that's
a huge mistake.