message: use constants for universal link hostnames in ember env
diff: 'use strict';
  +const {
  + MERCHANT_PAYMENT_UNIVERSAL_LINK_STAGING_HOSTNAME,
  + MERCHANT_PAYMENT_UNIVERSAL_LINK_HOSTNAME,
  +} = require('@cardstack/cardpay-sdk/index');
  +
  const infuraIdsByTarget = {
  staging: '558ee533522a468e9d421d818e06fadb', // this infura id is specific to https://app-staging.stack.cards/
  production: '5d6efa6b750b45459184cd11dd2c8697', // this infura id is specific to https://app.cardstack.com/
  };
  const universalLinkHostnamesByTarget = {
  - staging: 'https://wallet-staging.stack.cards',
  - production: 'https://wallet.cardstack.com',
  + staging: MERCHANT_PAYMENT_UNIVERSAL_LINK_STAGING_HOSTNAME,
  + production: MERCHANT_PAYMENT_UNIVERSAL_LINK_HOSTNAME,
  };
  const pkg = require('../package.json');
  @@ -21,7 +26,7 @@ module.exports = function (environment) {
  hubURL: process.env.HUB_URL,
  universalLinkDomain:
  universalLinkHostnamesByTarget[process.env.DEPLOY_TARGET] ??
  - 'https://wallet-staging.stack.cards',
  + MERCHANT_PAYMENT_UNIVERSAL_LINK_STAGING_HOSTNAME,
  version: pkg.version,
  sentryDsn: process.env.SENTRY_DSN,
  '@sentry/ember': {
  