Re: running logical replication as the subscription owner

I'm definitely in favor of making it easier to use logical replication
in a safe manner. In Citus we need to logically replicate and we're
currently using quite some nasty and undocumented hacks to do so:
We're creating a subscription per table owner, where each subscription
is owned by a temporary user that has the same permissions as the
table owner. These temporary users were originally superusers, because
otherwise we cannot make them subscription owners, but once assigning
a subscription to them we take away the superuser permissions from
them[1]. And we also need to hook into ALTER/DELETE subscription
commands to make sure that these temporary owners cannot edit their
own subscription[2].

Getting this right was not easy. And even it has the serious downside
that we need multiple subscriptions/replication slots which causes
extra complexity in various ways and it eats much more aggressively
into the replication slot limits than we'd like. Having one
subscription that could apply into tables that were owned by multiple
users in a safe way would make this sooo much easier.

[1]:
https://github.com/citusdata/citus/blob/main/src/backend/distributed/replication/multi_logical_replication.c#L1487-L1573
[2]: https://github.com/citusdata/citus/blob/main/src/backend/distributed/commands/utility_hook.c#L455-L487