Consider a tag

go.mod

@@ -88,7 +88,6 @@ require (
 	github.com/lnpay/lnpay-go v1.1.0
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/miekg/dns v1.1.58 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/prometheus/client_golang v1.19.0 // indirect

nostr.go

@@ -437,6 +437,14 @@ func CreateNostrReceipt(zapEvent nostr.Event, invoice string) (nostr.Event, erro
 		nip57Receipt.Tags = nip57Receipt.Tags.AppendUnique(*eTag)
 	}
 
+	if aTags := zapEvent.Tags.GetAll([]string{"a"}); aTags != nil {
+		for _, s := range aTags {
+			if s.Key() == "a" {
+				nip57Receipt.Tags = nip57Receipt.Tags.AppendUnique(s)
+			}
+		}
+	}
+
 	err = nip57Receipt.Sign(nostrPrivkeyHex)
 	if err != nil {
 		return nostr.Event{}, err