default OAuthSigner getRequestTokenSigner(String clientSecret) {
    OAuthHmacSigner signer = new OAuthHmacSigner();
    signer.clientSharedSecret = clientSecret;
    return signer;
  }
Returns the {@link OAuthSigner} for the initial token request
libraries/auth/src/main/java/org/datatransferproject/auth/OAuth1Config.java