show warning dialog when a legacy multi output descriptor is entered

src/main/java/com/sparrowwallet/sparrow/io/Descriptor.java

@@ -66,13 +66,18 @@ public class Descriptor implements WalletImport, WalletExport {
     @Override
     public Wallet importWallet(InputStream inputStream, String password) throws ImportException {
         try {
+            ByteArrayOutputStream baos = new ByteArrayOutputStream();
+            inputStream.transferTo(baos);
+            InputStream firstClone = new ByteArrayInputStream(baos.toByteArray());
+            InputStream secondClone = new ByteArrayInputStream(baos.toByteArray());
+
             try {
-                return PdfUtils.getOutputDescriptor(inputStream).toWallet();
+                return PdfUtils.getOutputDescriptor(firstClone).toWallet();
             } catch(Exception e) {
                 //ignore
             }
 
-            String outputDescriptor = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8)).lines().collect(Collectors.joining("\n"));
+            String outputDescriptor = new BufferedReader(new InputStreamReader(secondClone, StandardCharsets.UTF_8)).lines().collect(Collectors.joining("\n"));
             OutputDescriptor descriptor = OutputDescriptor.getOutputDescriptor(outputDescriptor.trim());
             return descriptor.toWallet();
         } catch(Exception e) {

src/main/java/com/sparrowwallet/sparrow/wallet/SettingsController.java

@@ -404,6 +404,10 @@ public class SettingsController extends WalletFormController implements Initiali
                 (walletForm.getWallet().getPolicyType() == PolicyType.MULTI ? "\nKey expressions are shown in canonical order." : ""));
         Optional<String> text = dialog.showAndWait();
         if(text.isPresent() && !text.get().isEmpty() && !text.get().equals(outputDescriptorString)) {
+            if(text.get().contains("(multi(")) {
+                AppServices.showWarningDialog("Legacy multisig wallet detected", "Sparrow supports BIP67 compatible multisig wallets only.\n\nThe public keys will be lexicographically sorted, and the output descriptor represented with sortedmulti.");
+            }
+
             setDescriptorText(text.get().replace("\n", ""));
         }
     }