Update PGBouncer HA docs
Update the PGBouncer portion of HA database documentation. Update based on findings from your testing:
- Which steps did you get hung up on?
- How did you troubleshoot?
- How can the next person avoid this problem?
The end goal is for someone who has never gone through the setup process to get through it without any problems. PGBouncer tends to be a problem spot during setup. What steps can we add to absolutely validate that the setup is working?