Builts the auth url to an IdP using PKCE flow

pkce_first_step.js

const PKCEAuthCodeFirstStep = () => {
  let oidcURL = `${process.env.OIDC_IDP_URL}/auth`;
  let queryParams = [`client_id=${process.env.OIDC_CLIENT_ID}`];
  let codeVerifier = createCodeVerifier( 50 );
  localStorage.setItem( 'code_verifier', codeVerifier );

  return createCodeChallenge( codeVerifier ).then( codeChallenge => {
    queryParams.push(`code_challenge=${codeChallenge}`);
    queryParams.push(`redirect_uri=http://localhost/login_oidc`);
    queryParams.push(`code_challenge_method=S256`);
    queryParams.push(`response_type=code`);
    queryParams.push(`scope=openid`);

    return `${oidcURL}?${queryParams.join("&")}`;
  } );
}