Summary:
Ref T11044. I'm going to hold this until after the release cut, but I think it's good to go.
This allows installs to configure multiple masters in `cluster.databases` and partition applications across them (for example, put Maniphest on a dedicated database).
When we make a Maniphest connection we go look up which master we should be hitting first, then connect to it.
This has at least approximately been planned for many years, so the actual change is largely just making sure that your config makes sense.
Test Plan:
- Configured `db001.epriestley.com` and `db002.epriestley.com` as master/master.
- Partitioned applications between them.
- Interacted with various applications, saw writes go to the correct host.
- Viewed "Database Servers" and saw partitioning information.
- Ran schema upgrades.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T11044
Differential Revision: https://secure.phabricator.com/D16876
