Fix: Ensure Done() is called on external wallets even on errors

Use defer to guarantee that Done() is called on all external wallet signers
regardless of whether errors occur during signature collection, auditing,
or approval phases. This prevents resource leaks when the endorsement
process fails early.

Previously, if requestSignaturesOnIssues or requestSignaturesOnTransfers
returned an error, any external wallets already added to the map would
not have their Done() method called, potentially leaving resources uncleaned.

Author: AKRAM@il.ibm.com

token/services/ttx/collectendorsements.go

@@ -84,6 +84,17 @@ func (c *CollectEndorsementsView) Call(context view.Context) (interface{}, error
 	metrics := GetMetrics(context)
 
 	externalWallets := make(map[string]ExternalWalletSigner)
+	
+	// Ensure Done() is called on all external wallets regardless of errors
+	defer func() {
+		logger.DebugfContext(context.Context(), "Inform external wallets that endorsement is complete")
+		for id, signer := range externalWallets {
+			if err := signer.Done(); err != nil {
+				logger.ErrorfContext(context.Context(), "failed to signal done external wallet [%s]", id)
+			}
+		}
+	}()
+
 	// 1. First collect signatures on the token request
 	issueSigmas, err := c.requestSignaturesOnIssues(context, externalWallets)
 	if err != nil {
@@ -95,15 +106,6 @@ func (c *CollectEndorsementsView) Call(context view.Context) (interface{}, error
 		return nil, errors.WithMessagef(err, "failed requesting signatures on transfers")
 	}
 
-	// signal the external wallets that the process is completed
-	logger.DebugfContext(context.Context(), "Inform external wallets that endorsement is complete")
-	for id, signer := range externalWallets {
-		if err := signer.Done(); err != nil {
-			logger.ErrorfContext(context.Context(), "failed to signal done external wallet [%s]", id)
-			logger.Errorf("failed to signal done external wallet [%s]", id)
-		}
-	}
-
 	// Add the signatures to the token request
 	logger.DebugfContext(context.Context(), "Add the signatures to the token request")
 	if !c.tx.TokenRequest.SetSignatures(mergeSigmas(issueSigmas, transferSigmas)) {