db migrations

[smnorris]

Add scripts for db migration.

• tear down and rebuild on every schema change is very inefficient
• manually applying spot changes to multiple database instances is error prone

Alembic seems like a good candidate.

[smnorris]

I'm still not sure additional tooling for db migration is worth it. I think db schema upgrades could be done something like below, the log data is the only info that is retained between model runs:

1. optionally, dump any log data worth retaining
2. drop bcfishpass schema
3. recreate bcfishpass schema by executing all files in /db
4. optionally, re-load log

I think the only changes required are:

• move or rename any objects created in /db, ensuring everything is in bcfishpass schema
• split up jobs/setup - creating separate scripts for creating db objects in bcfishpass schema vs everything else
• optionally, create an upgrade script that does all this and handles the log retention

Down sides to this approach:

• because everything is re-created, access permissions would also have to be redefined on every schema change
• db downtime on every schema change
• rebuilding materialized views is slow when all source data have been loaded (fptwg_assmt_wsd_summary_vw.sql)
• probably more?