## Problem
We need a flag to require proxy protocol (prerequisite for #5416)
## Summary of changes
Add a cli flag to require client IP addresses. Error if IP address is
missing when the flag is active.
## Problem
these JoinSets live for the duration of the process. they might have
many millions of connections spawned on them and they never get cleared.
Fixes#4672
## Summary of changes
Drain the connections as we go
## Problem
It took me a while to understand the purpose of all the tasks spawned in
the main functions.
## Summary of changes
Utilising the type system and less macros, plus much more comments,
document the shutdown procedure of each task in detail
As soon as we have received the SSLRequest packet, and have figured
out the hostname to connect to from the SNI, we can start passing
through data. We don't need to parse the StartupPacket that the client
will send next.
In order to not to create NodePorts for each compute we can setup
services that accept connections on wildcard domains and then use
information from domain name to route connection to some internal
service. There are ready solutions for HTTPS and TLS connections
but postgresql protocol uses opportunistic TLS and we haven't found
any ready solutions.
This patch introduces `pg_sni_router` which routes connections to
`aaa--bbb--123.external.domain` to `aaa.bbb.123.internal.domain`.
In the long run we can avoid console -> compute psql communications,
but now this router seems to be the easier way forward.
