Implement Extended Query PostgreSQL Protocol

[alex-dukhno]

If I were asked to describe what is "Extended Query PostgreSQL Protocol", I'd say it is Prepared Statement over wire.
As far as I understand (right now) query is sent in form of the string like select * from table where col1 = $1; or insert into table values ($1, $2, $3); and then data bindings negotiated between client and server.

Doc https://www.postgresql.org/docs/12/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY

Quick search over Materialize source code gave me https://github.com/MaterializeInc/materialize/blob/main/src/pgwire/src/protocol.rs#L114 as possible entry point to start getting info of how "prepared statement" state could be managed

[silathdiir]

Hi @alex-dukhno , I'd like to work on this issue after PR #184 is reviewed and merged. Please assign it to me. Thanks.