Processes a payment in the store for a given user's cart. This implementation
processes a request through PayPal Payflow Link. Phone numbers and emails
are taken out of the request as those are validated by PayPal and may cause
inconvenient errors. Use comment1 and comment2 to send emails and phone
numbers instead. If the transaction is declined a result code of 10000 is
returned, otherwise the result code sent back from PayPal is returned.
parameters - A Map containing the values of the user's
submitted payment information.
A Map containing a least one key named
"resultCode", which contains a String parsable into an int,
representing the results of the processing. 0 for the resultCode
indicates success. Optionally, the Map may include
additional keys, such as "resultMessage", a string describing the
results of the processing.