Upgrade Postgresql in development and staging

[ddohler]

AWS is end-of-life-ing Postgresql 9.6, and will forcibly upgrade us to version 12 after ~January 18th~ April 26th.

Further details: https://forums.aws.amazon.com/ann.jspa?annID=8499

[KlaasH]

Per discussion in RRP, I changed this from a "do the whole thing" task to a "development and staging" one. So the pieces are:

• Upgrade the dev environment
• Test in development and make any necessary code or configuration changes. Hopefully the code is fine. This is all a bit simpler if we just need to upgrade RDS and don't need a code deploy.
• Draft a checklist for upgrading the staging RDS instance
• Follow the checklist to upgrade staging. Note: If there are code changes needed, push a test branch to get them deployed to staging (or do it manually, but that's more work and I'm not sure there'd be any advantage to it).

The outcome of this task should be that development and staging are fully upgraded and we have a checklist to follow for upgrading production.

[KlaasH]

I got as far as getting my local instance running with an upgraded database container and pushing a test branch (test/postgres-13-upgrade). Then I spent some time trying to figure out why Jenkins wasn't building it, then I discovered that the deadline had been extended and put this down.

Apparently Jenkins did end up trying to build the branch, several weeks after I pushed it up, though it didn't succeed. That one looked simple, so I've just pushed a change that might fix it, but there might also be more lurking in the shadows.

[BryanQuigley]

Jenkins does not run this using Vagrant - which means we need to either upgrade Jenkins or migrate this to GH actions. Happy to run with migrate to GH actions.