sales-invoices GET API

GET endpoints related to sales-invoices.

• sales-invoices-by-customer-get
• sales-invoices-by-entity-get
• sales-invoices-by-id-get
• sales-invoices-by-payment-status-get
• sales-invoices-by-receipt-number-get
• sales-invoices-by-status-get
• sales-invoices-get