def verify(raw_body, key)
      _, plaintext, signature = parse(raw_body)
      key.public_key.verify(digest, signature, plaintext)
    rescue OStatus2::BadSalmonError
      false
    end
def verify(raw_body, key)
      _, plaintext, signature = parse(raw_body)
      key.public_key.verify(digest, signature, plaintext)
    rescue OStatus2::BadSalmonError
      false
    end
Verify the magical envelope's integrity
 @param [String] raw_body Magical envelope
 @param [OpenSSL::PKey::RSA] key The public part of the key will be used
 @return [Boolean]