Status-Line The first line of a Response message is the Status-Line, consisting of the protocol version followed by a numeric status code and its associated textual phrase, with each element separated by SP characters. No CR or LF is allowed except in the final CRLF sequence.
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF status code vs status in body https://www.codetinkerer.com/2015/12/04/choosing-an-http-status-code.html
https://httpstatuses.com/
The main choice is do you want to treat the HTTP status code as part of your REST API or not.