Ref T8726. The only notable bit here is that the "body" / "title" fields (which are currently shared across a bunch of types) are getting split into application variants.

Among other things, this will let us label the field "Commit message" for commits, for example.

• Created a rule using all four fields.
• Applied patch, saw rule break ("unknown field").
• Ran storage upgrade, saw rule fix itself in the migration.
• Edited tasks, triggered rule, viewed transcripts.