This commit modifies the new payment module within the database to
match the coding style of the rest of the package and the project as a
hole. Additionally, a few fields have been renamed, and the extra
timestamp added to the OutgoingPayment struct has been removed as
there’s already a CreationTime field within the Invoice struct that’s
embedded within the OutgoingPayment struct.
Go-fmt files. Refactored code according to the guidelines.
Enhanced payment test: add error checking
and individual context for each API call.
Add Timestamp field to payment struct.
