fix: duplicate issuers (#2128)

pkg/postage/service.go

@@ -78,6 +78,12 @@ func NewService(store storage.StateStorer, postageStore Storer, chainID int64) (
 func (ps *service) Add(st *StampIssuer) {
 	ps.lock.Lock()
 	defer ps.lock.Unlock()
+
+	for _, v := range ps.issuers {
+		if bytes.Equal(st.data.BatchID, v.data.BatchID) {
+			return
+		}
+	}
 	ps.issuers = append(ps.issuers, st)
 }
 
@@ -85,8 +91,6 @@ func (ps *service) Add(st *StampIssuer) {
 // a batch creation event from the blockchain listener to ensure that if a stamp
 // issuer was not created initially, we will create it here.
 func (ps *service) Handle(b *Batch) {
-	_, err := ps.GetStampIssuer(b.ID)
-	if errors.Is(err, ErrNotFound) {
 	ps.Add(NewStampIssuer(
 		"recovered",
 		string(b.Owner),
@@ -97,7 +101,6 @@ func (ps *service) Handle(b *Batch) {
 		b.Start,
 		b.Immutable,
 	))
-	}
 }
 
 // StampIssuers returns the currently active stamp issuers.