Stringified UUID-based DS keys should not be wrapped in JSON

[yuri-sergiichuk]

Some of the kind keys, e.g. InboxMessage kind key, use UUID as the key value, but they do store the key value as Stringified JSON message in the storage, e.g.: spine.server.delivery.InboxMessage name:{"uuid":"4c16b7d2-06ff-4280-ba0e-14ffdb9aff3a"}

The problem with such a key format is that any key has the same prefix "uuid":" which clashes with the Datastore best practices.

The better solution here is to use only the UUID value: 4c16b7d2-06ff-4280-ba0e-14ffdb9aff3a