PSA: Planning to grease protocol connections during 19beta

I want to make sure this doesn't take anyone by surprise: I'm planning
to get Jelte's "grease" patch into shape for a commit some time in
January.

https://commitfest.postgresql.org/patch/6157/

If you're unfamiliar with the concept of greasing [1], one way to
think of it is that we're inverting Postel's Law: we will be very
liberal in what we send during connection, and then fail the
connection outright if a server doesn't reply with a
NegotiateProtocolVersion that points out our nonsense. This helps
build confidence that a future bump in our protocol defaults won't
cause operational failures due to buggy implementations (proxies,
bouncers, other servers).

The plan is to grease the minor version number and at least one
protocol extension during the 19 beta, then revert partway through (as
tracked by a mid-beta Open Item). Users who run into trouble during
beta can revert to the previous behavior by setting
max_protocol_version=3.0, ideally *after* they file a bug report for
the peer implementation. Documenting that, in a way that's effective
for both users and implementers, is something that still needs work
for the current patchset.

So, if anyone has objections to the overall idea, now is a great time
to say so. (Here is fine, but preferably also on the patch thread for
posterity.)

Thanks!
--Jacob

[1] https://datatracker.ietf.org/doc/draft-edm-protocol-greasing/