Goal: Enable customers to use Postgres connection pooling via pgBouncer in a supported way with Quay.

Why is this important: pgbouncer is a popular PostgreSQL connection pooler which is often used in larger environment to contain the resource requirements induced by Quay and Clair which require a large amount of open database connections.

We currently do not test it and thus do not provide not guidance in our docs and as such no official suport. We don't have any instructions as to how pgpouncer is supposed to work with Quay or what issues we might expect when using it on scale. We would like to add official support for pgbouncer along with a sample configuration from a vendor.

Acceptance criteria:

• a vendor supported pgBouncer configuration is permanently established in the QE environment
• Quay's standard test suite is successfully executed against a pgBouncer-enabled  database setup
• the tested pgBouncer configuration is part of our documentation
• pgBouncer (including vendor and version name) appear in our tested integration matrix)