Event Module to include a separate donation line item (to a different fund) in the 'Add fees/payments' function.

Currently, the external event registration form allows a registrant to add a separate donation, in addition to their event registration. This is all configured when building out the event and allows an Org to allocate the donation to a different Campaign/Fund/Appeal than the event registration payment. Receipting function is also unique to the donation.

Unfortunately this feature does not carry over to the back-end while running an event, checking in registrants and utilizing the 'Add fees/payments' function. It would be helpful to have the donation feature added here as well - with the unique Campaign/Fund/Appeal allocation so the Org only has to charge the registrant once, and not do extra back-end cleanup to allocate the funds. It it too time consuming and not customer friendly to have to run two separate transactions, especially when timing is tight at event check-in.