mark_as_paid: Mark as Paid
In ebinabo/paystack: Paystack API

This marks an invoice as paid in cases where it was paid offline

1	mark_as_paid(authorization, invoice_id, ...)

`authorization`	set_keys("", "SECRET_KEY")$secret, equivalent of "-H Authorization: Bearer SECRET_kEY"
`...`	Body Params
`amount_paid`	int32. REQUIRED Amount paid by customer
`paid_by`	string. REQUIRED The email address of the customer
`payment_date`	string. REQUIRED Date payment was made
`payment_method`	string. REQUIRED The method of payment which are "Cash", "POS", "Cheque", "Bank Transfer" or "Other"
`note`	string. An optional note