Blueprint v1 API extension

[croissanne]

This discussion details how we'll extend the v1 API to support blueprints. The existing API should of course not be broken, and a single-request /compose should still be supported.

The obvious addition is a CRUD on /blueprints(/{id}).

Also a GET and POST on /blueprints/{id}/composes to get composes, and create a new compose based on a blueprint.

/blueprints/{id}/(export|import) ?

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Composes should still be useable standalone, so the blueprint-id field in each compose should be nullable.

/blueprints/{id}/composes/{id}(/clones) should currently not be added I think, maybe in v2. But I think we can just keep using /composes/{id} for now.

[croissanne]

Versioning:

We should always default to the latest version for create/update (delete applies to all of course). But it might be necessary to get read-only access to old versions.

So maybe a ?version= query parameter?