idea: Payments for invoices

[TreyWW]

Integrate with payment gateways for clients to pay invoices online.
Track payment statuses (paid, pending, overdue, etc.).
Generate payment links for each invoice ID.

Preconditions:

#4 must be finished

Acceptance Criteria:

• please do task a
• please do task b

Definition of Done:

• code has been tested
• all tasks are completed

[TreyWW]

On hold while we get invoices finished. Mainly #39, just make sure we have fully functional invoice creation