Updates the attributes for an authenticated user in the Zephr user store.

Updates the attributes for an authenticated user in the Zephr user store. The behaviour for the POST and PATCH methods on this endpoint is identical. The provided attributes are saved for the user. Any new attributes are added. Any existing attributes with the same keys are updated. Any existing attributes with different keys remain unchanged. The request can also include an optional 'blaize-validator' property to authenticate a previously partially registered user.