title: Representing Multiple Payment Methods
body: <p>I have a situation where customers are able to pay via either a credit card or by a PayPal account. I currently have a super class as 'customer' with two sub-types of 'public' and 'commercial'. However, both types can pay by either form of payment, as well as have multiple credit cards / PayPal accounts associated with them.</p>
  
  <p>I have a current model that works, but not for having multiple cards etc. I eventually need to be able to query what customer paid by what method. For example, how many customers during a time period paid via credit card.</p>
  
  <p>The model minus the payment details look's similar to:</p>
  
  <p>[ORDER]-----[CUSTOMER]---(D)---[PUBLIC][COMMERCIAL]</p>