Use spqr-specific (patched) PostgreSQL version

[reshke]

There are various reasons to use better version of PostgreSQL to run in cloud environments.

For spqr, number of improvements needed to provide some features of unsharded base-metal PostgreSQL instance

1.) Cloud service auth feature to allow SCRAM auth in proxy-mode (to perform SCRAM backend auth under specified role without its plain text password), see commit

2.) Cluster-wide snapshots and intelligent cross-shard queries support using Commit Sequence Number patch (rebased last version from pgsql-hackers on PG_16), refer to pr

https://github.com/pg-sharding/cpg

[Denchick]

Hi! Nice idea but we have to provide backward compatibility with upstream postgres

[reshke]

no we dont
we can use feature flag to resolve if we use patched/unpatched version