Re-implement testing API using tagged template literals

[ianwalter]

const { test, tag } = require('@ianwalter/bff')

test`

Submitting an order when an existing user is coming from a partner site and 
is using a coupon code linked to a different partner should still link the order 
to the original, referring partner

${tag`production`} ${lowerEnvironments}

${async t => {
  // Test logic goes here.
}}
`

test.skip`TODO: add test for submitting an order when product is white labeled`