func ComputeDetachedSignature(content, tokenID, tokenSecret string) (string, error)
ComputeDetachedSignature takes content and token details and computes a detached JWS signature. This is described in Appendix F of RFC 7515. Basically, this is a regular JWS with the content part of the signature elided.
func DetachedTokenIsValid(detachedToken, content, tokenID, tokenSecret string) bool
DetachedTokenIsValid checks whether a given detached JWS-encoded token matches JWS output of the given content and token