优化结构

internal/biz/payment/payment_order.go

@@ -182,6 +182,15 @@ func (r *PaymentOrderSourceRegistry) Source(kind string) PaymentOrderSource {
 	return r.sources[kind]
 }
 
+func (r *PaymentOrderSourceRegistry) Len() int {
+	if r == nil {
+		return 0
+	}
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	return len(r.sources)
+}
+
 func (r *PaymentOrderSourceRegistry) Unregister(kind string) {
 	if r == nil {
 		return