Checks a token rotation body (sections 6.1 and 6.1.1): no content, or { key }.
{ key }
the parsed JSON body
Optional
whether the request carried a body
{ ok: true, key } (null for no new key), or a refusal
{ ok: true, key }
Checks a token rotation body (sections 6.1 and 6.1.1): no content, or
{ key }.