Feature request: Add support for separate stats user for `pgbouncer-exporter`

[Cute-Monster]

Currently, pgbouncer-exporter is using admin credentials used by pgbouncer container itself.

https://github.com/icoretech/helm/blob/e1f4a414d1014012ebb823bbb693a3482eedbfcd/charts/pgbouncer/templates/deployment.yaml#L144C9-L153

In some cases, when using AWS RDS database with master password managed by RDS itself, it may contain special characters which can cause the following golang error --> net/url: invalid userinfo

PR raised to add this feature --> #30

[masterkain]

Thanks again for filing this, and for the proposed PR! Looking into it a bit more we realised the root cause was the exporter URL embedding the credentials directly. Helm’s templating happily renders those verbatim, but net/url will choke as soon as the password contains characters such as @ or / – which is what happens with the AWS-managed RDS secrets.

Instead of introducing parallel secrets, we taught the chart to let the exporter rely on the lib/pq fallbacks. The DSN no longer contains inline credentials, and we ship the existing admin user/password via both PGBOUNCER_* (for backwards compatibility) and PG* env vars. PgBouncer itself keeps working exactly as before.

We verified the change end-to-end:

• helm template renders the manifests with and without special characters, falling back cleanly to the existing secret.
• Full Docker smoke tests cover three cases: a standard exporter deployment, a password with special characters (pa:ss@word/?$&), and a DaemonSet-style layout that reaches PgBouncer over localhost. In each case the exporter comes up cleanly and keeps serving metrics.

This is now in main as 3.1.1. Please shout if you spot anything we missed, and thanks for helping make the chart more robust!