title: Stripe - retrieve Customer ID using email from form
body: <p>Is there any way to retrieve a Customer ID from the e-mail they enter in the payment form via the API? </p>
  
  <p>For my application customers will pay multiple times on an ongoing basis but for simplicity's sake there are no logins, they just enter their payment info and invoice number. As a best practice I'd like to keep all of their charges together in Stripe for obvious reasons but it doesn't seem this is possible?</p>