">Section&nbsp;6 of [RFC7231]</a> requires recipients to treat unknown 3xx
   status codes the same way as status code 300 Multiple Choices
   (<a href="./rfc7231#section-6.4.1">[RFC7231], Section&nbsp;6.4.1</a>).  Thus, servers will not be able to rely
   on automatic redirection happening similar to status codes 301, 302,
   or 307.

   Therefore, initial use of status code 308 will be restricted to cases
   where the server has sufficient confidence in the client's
   understanding the new code or when a