Depends on D18848. Ref PHI243. This puts a bit of logic up front to figure out the blueprint type before we actually start editing it.

This implementation is a little messy but it keeps the API clean. Eventually, the implementation could probably go in the TransactionTypes so more code is shared, but I'd like to wait for a couple more of these first.

This capability probably isn't too useful, but just pays down a bit of technical debt from the caveat introduced in D18822.

• Created a new blueprint with the API.
• Tried to create a blueprint without a "type" (got a helpful error).
• Created and edited blueprints via the web UI.
• Tried to change the "type" of an existing blueprint (got a helpful error).