docs: add comments for payment calculations and headers

Author: dorzepowski

pkg/internal/payctx/payment_context.go

@@ -7,7 +7,7 @@ import (
 )
 
 // Payment holds information about a processed payment stored in the request context
-type Payment struct { //nolint: revive // Ignore that struct starts with package name
+type Payment struct {
 	// SatoshisPaid is the amount paid in satoshis
 	SatoshisPaid int
 	// Accepted indicates whether the payment was accepted

pkg/middleware/payment_middleware.go

@@ -10,6 +10,7 @@ import (
 )
 
 const (
+	// HeaderPaymentPaid is the name of the header with confirmation of the payed amount.
 	HeaderPaymentPaid = payment.HeaderSatoshisPaid
 )
 
@@ -28,6 +29,7 @@ func WithPaymentLogger(logger *slog.Logger) func(*PaymentMiddlewareConfig) {
 	}
 }
 
+// WithRequestPriceCalculator sets a custom function to calculate the price of a request in satoshis for a payment middleware.
 func WithRequestPriceCalculator(calculator func(r *http.Request) (int, error)) func(*PaymentMiddlewareConfig) {
 	if calculator == nil {
 		panic("calculator must be provided")