def validation_key(client_id = nil, client_secret = nil)
    hdrs = client_id && client_secret ?
        { "authorization" => Http.basic_auth(client_id, client_secret)} : {}
    json_get(target, "/token_key", key_style, hdrs)
  end
def validation_key(client_id = nil, client_secret = nil)
    hdrs = client_id && client_secret ?
        { "authorization" => Http.basic_auth(client_id, client_secret)} : {}
    json_get(target, "/token_key", key_style, hdrs)
  end
Gets the key from the server that is used to validate token signatures. If
 the server is configured to use a symetric key, the caller must authenticate
 by providing a a +client_id+ and +client_secret+. If the server
 is configured to sign with a private key, this call will retrieve the
 public key and +client_id+ must be nil.
 @param (see Misc.server)
 @return [Hash]