[codbex-payment-invoice-ext] Add generating Purchase Invoice Payment and fix Sales Invoice Payment

[NicoleNG18]

Implement functionality that allows users to attach payments to sales or purchase invoices. Only display unpaid invoices for the logged-in user, filtered by the same currency. Once selected, generate the corresponding sales or purchase invoice payment and attach it to the appropriate invoice.

[NicoleNG18]

Fixed with:

• add supplier to supplier payment codbex-payments#41
• Add feature for attaching payments to sales/purchase invoices codbex-payment-invoice-ext#5