Add info for unhandled exception

dart/lib/src/sentry_envelope.dart

@@ -13,14 +13,18 @@ import 'sentry_user_feedback.dart';
 
 /// Class representation of `Envelope` file.
 class SentryEnvelope {
-  SentryEnvelope(this.header, this.items);
+  SentryEnvelope(this.header, this.items, {this.containsUnhandledException = false});
 
   /// Header describing envelope content.
   final SentryEnvelopeHeader header;
 
   /// All items contained in the envelope.
   final List<SentryEnvelopeItem> items;
 
+  /// Whether the envelope contains an unhandled exception.
+  /// This is used to determine if the native SDK should start a new session.
+  final bool containsUnhandledException;
+
   /// Create a [SentryEnvelope] containing one [SentryEnvelopeItem] which holds the [SentryEvent] data.
   factory SentryEnvelope.fromEvent(
     SentryEvent event,
@@ -29,6 +33,8 @@ class SentryEnvelope {
     SentryTraceContextHeader? traceContext,
     List<SentryAttachment>? attachments,
   }) {
+    final isUnhandledException =
+        event.exceptions?.first.mechanism?.handled == false;
     return SentryEnvelope(
       SentryEnvelopeHeader(
         event.eventId,
@@ -41,6 +47,7 @@ class SentryEnvelope {
         if (attachments != null)
           ...attachments.map((e) => SentryEnvelopeItem.fromAttachment(e))
       ],
+      containsUnhandledException: isUnhandledException,
     );
   }
 

flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt

@@ -355,8 +355,9 @@ class SentryFlutterPlugin : FlutterPlugin, MethodCallHandler, ActivityAware {
     val args = call.arguments() as List<Any>? ?: listOf()
     if (args.isNotEmpty()) {
       val event = args.first() as ByteArray?
-      if (event != null && event.isNotEmpty()) {
-        val id = InternalSentrySdk.captureEnvelope(event)
+      val containsUnhandledException = args[1] as Boolean
+      if (event != null && event.isNotEmpty() && containsUnhandledException != null) {
+        val id = InternalSentrySdk.captureEnvelope(event, containsUnhandledException)
         if (id != null) {
           result.success("")
         } else {

flutter/lib/src/file_system_transport.dart

@@ -19,7 +19,7 @@ class FileSystemTransport implements Transport {
     await envelope.envelopeStream(_options).forEach(envelopeData.addAll);
     try {
       // TODO avoid copy
-      await _native.captureEnvelope(Uint8List.fromList(envelopeData));
+      await _native.captureEnvelope(Uint8List.fromList(envelopeData), envelope.containsUnhandledException);
     } catch (exception, stackTrace) {
       _options.logger(
         SentryLevel.error,

flutter/lib/src/native/sentry_native_binding.dart

@@ -16,7 +16,7 @@ abstract class SentryNativeBinding {
 
   Future<NativeAppStart?> fetchNativeAppStart();
 
-  Future<void> captureEnvelope(Uint8List envelopeData);
+  Future<void> captureEnvelope(Uint8List envelopeData, bool isUnhandledException);
 
   Future<void> beginNativeFrames();
 

flutter/lib/src/native/sentry_native_channel.dart

@@ -80,8 +80,9 @@ class SentryNativeChannel
   }
 
   @override
-  Future<void> captureEnvelope(Uint8List envelopeData) =>
-      _channel.invokeMethod('captureEnvelope', [envelopeData]);
+  Future<void> captureEnvelope(Uint8List envelopeData, bool containsUnhandledException) {
+    return _channel.invokeMethod('captureEnvelope', [envelopeData, containsUnhandledException]);
+  }
 
   @override
   Future<Map<String, dynamic>?> loadContexts() =>