+=item apply_payments_and_credits [ OPTION => VALUE ... ]
+
+Applies unapplied payments and credits to this invoice.
+
+A hash of optional arguments may be passed. Currently "manual" is supported.
+If true, a payment receipt is sent instead of a statement when
+'payment_receipt_email' configuration option is set.
+
+If there is an error, returns the error, otherwise returns false.