428 Precondition Required response status code
indicates that the server requires the request to be conditional.
Typically, this means that a required precondition header, such
If-Match, is missing.
When a precondition header is not matching the server side state, the
response should be
428 Precondition Required
|RFC 6585, section 3: 428 Precondition Required||Additional HTTP Status Codes|