anchor.diff:  
   . A user enter's his/her payment details on a merchant site.
   
  -. The merchant site invokes the `GoCardlessCheckoutServlet` (this is explained below).
  +. The merchant site invokes the `GoCardlessCheckoutServlet`.
   
   . The `GoCardlessCheckoutServlet` invokes the `GoCarldessPlugin#buildFormDescriptor`.
   
   . The `GoCarldessPlugin#buildFormDescriptor` method invokes the `redirectFlows().create()`. This *initiates* the *GoCardless redirect flow*  and returns the *redirect URL* .
   
  -. The merchant site redirects the user to this URL and the user manually confirms setting up the mandate on this page.
  -
  -. GoCardless redirects the user to the *success page*. This invokes the `KillBill#addPaymentMethod` which in turn invokes `GoCardlessPlugin#addPaymentMethod`.
  +. The merchant site redirects the user to this URL 
  +
  +* The user manually enters bank details on this page.
  +
  +. GoCardless redirects the user to the *success page*. 
  +
  +* This invokes the `KillBill#addPaymentMethod` which in turn invokes `GoCardlessPlugin#addPaymentMethod`.
   
   . The `GoCarldessPlugin#addPaymentMethod` invokes `redirectFlows().complete`. This *completes* the *redirect flow* and returns the *mandate id* which is saved in the Kill Bill database.
   
  
positive.code: 
  *Kill Bill* - The Kill Bill system
  
  *GoCardless Plugin*:  Payment plugin corresponding to GoCardless that can process payments using the GoCardless system
  
  *GoCardless*: The GoCardless payment system
  
negative.code: 
  . The merchant site redirects the user to this URL. 
  
  . The user *manually*  enters bank details at this page.
  
  . If successful, GoCardless redirects the user to the *success page URL* sent to it in step 1. 
  
  