How does this work in terms of Postgres connections/pools? My understanding of this is that you'd do something like `SET SESSION user_id TO 123;` which sets the variable `user_id` for that connection. Subsequent queries could use that variable to do row-based authorization but they need to use the same connection. Is this how Postgrest does it? (guaranteeing the same connection for the lifecycle of a request that is)
IIRC postgrest starts a transaction for each request, and inside of that sets the variables. I've done some testing to make sure that variables do not leak between requests.
