code: func certsHandler(c *router.Context) {
  	s := GetSigner(c.Context)
  	if s == nil {
  		httpReplyError(c, http.StatusNotFound, "No Signer instance available")
  		return
  	}
  	certs, err := s.Certificates(c.Context)
  	if err != nil {
  		httpReplyError(c, http.StatusInternalServerError, fmt.Sprintf("Can't fetch certificates - %s", err))
  	} else {
  		httpReply(c, http.StatusOK, certs)
  	}
  }
docs: // certsHandler servers public certificates of the signer in the context.