These were needed before as a way to _partially deserialize_
blueprints. Indeed, some commands required accessing information of
the blueprint, but not necessarily the schema. So out of laziness (or
cleverness?), we only deserialized validators as serde::Value and
achieved that through the use of generics.
Now that validators and schemas have proper deserialisers, we can
simply deserialize a blueprint.
TODO: Our serialisation/deserialisation is safe with regards to
itself; i.e. it roundtrips. However, we only supports a subset of the
specified blueprint format. For example, we would fail to deserialize
blueprints that have inline data-schemas (we only use references).