add sampled flag

dart/lib/src/sentry_baggage.dart

@@ -188,6 +188,10 @@ class SentryBaggage {
     set(_sampleRateKeyName, value);
   }
 
+  void setSampled(String value) {
+    set('sentry-sampled', value);
+  }
+
   double? getSampleRate() {
     final sampleRate = get(_sampleRateKeyName);
     if (sampleRate == null) {

dart/lib/src/sentry_trace_context_header.dart

@@ -12,6 +12,7 @@ class SentryTraceContextHeader {
     this.userSegment,
     this.transaction,
     this.sampleRate,
+    this.sampled,
   });
 
   final SentryId traceId;
@@ -22,6 +23,7 @@ class SentryTraceContextHeader {
   final String? userSegment;
   final String? transaction;
   final String? sampleRate;
+  final String? sampled;
 
   /// Deserializes a [SentryTraceContextHeader] from JSON [Map].
   factory SentryTraceContextHeader.fromJson(Map<String, dynamic> json) {
@@ -34,6 +36,7 @@ class SentryTraceContextHeader {
       userSegment: json['user_segment'],
       transaction: json['transaction'],
       sampleRate: json['sample_rate'],
+      sampled: json['sampled'],
     );
   }
 
@@ -48,6 +51,7 @@ class SentryTraceContextHeader {
       if (userSegment != null) 'user_segment': userSegment,
       if (transaction != null) 'transaction': transaction,
       if (sampleRate != null) 'sample_rate': sampleRate,
+      if (sampled != null) 'sampled': sampled,
     };
   }
 
@@ -76,7 +80,9 @@ class SentryTraceContextHeader {
     if (sampleRate != null) {
       baggage.setSampleRate(sampleRate!);
     }
-
+    if (sampled != null) {
+      baggage.setSampled(sampled!);
+    }
     return baggage;
   }
 

dart/lib/src/sentry_tracer.dart

@@ -346,6 +346,7 @@ class SentryTracer extends ISentrySpan {
       transaction:
           _isHighQualityTransactionName(transactionNameSource) ? name : null,
       sampleRate: _sampleRateToString(_rootSpan.samplingDecision?.sampleRate),
+      sampled: _rootSpan.samplingDecision?.sampled.toString(),
     );
 
     return _sentryTraceContextHeader;

dart/test/protocol/sentry_baggage_header_test.dart

@@ -20,11 +20,12 @@ void main() {
       baggage.setUserSegment('userSegment');
       baggage.setTransaction('transaction');
       baggage.setSampleRate('1.0');
+      baggage.setSampled('false');
 
       final baggageHeader = SentryBaggageHeader.fromBaggage(baggage);
 
       expect(baggageHeader.value,
-          'sentry-trace_id=$id,sentry-public_key=publicKey,sentry-release=release,sentry-environment=environment,sentry-user_id=userId,sentry-user_segment=userSegment,sentry-transaction=transaction,sentry-sample_rate=1.0');
+          'sentry-trace_id=$id,sentry-public_key=publicKey,sentry-release=release,sentry-environment=environment,sentry-user_id=userId,sentry-user_segment=userSegment,sentry-transaction=transaction,sentry-sample_rate=1.0,sentry-sampled=false');
     });
   });
 }

dart/test/sentry_trace_context_header_test.dart

@@ -14,6 +14,7 @@ void main() {
       'user_segment': 'user_segment',
       'transaction': 'transaction',
       'sample_rate': '1.0',
+      'sampled': 'false'
     };
     final context = SentryTraceContextHeader.fromJson(mapJson);
 
@@ -26,6 +27,7 @@ void main() {
       expect(context.userSegment, 'user_segment');
       expect(context.transaction, 'transaction');
       expect(context.sampleRate, '1.0');
+      expect(context.sampled, 'false');
     });
 
     test('toJson', () {
@@ -38,7 +40,7 @@ void main() {
       final baggage = context.toBaggage();
 
       expect(baggage.toHeaderString(),
-          'sentry-trace_id=${id.toString()},sentry-public_key=123,sentry-release=release,sentry-environment=environment,sentry-user_id=user_id,sentry-user_segment=user_segment,sentry-transaction=transaction,sentry-sample_rate=1.0');
+          'sentry-trace_id=${id.toString()},sentry-public_key=123,sentry-release=release,sentry-environment=environment,sentry-user_id=user_id,sentry-user_segment=user_segment,sentry-transaction=transaction,sentry-sample_rate=1.0,sentry-sampled=false');
     });
   });
 }

dart/test/sentry_tracer_test.dart

@@ -489,6 +489,7 @@ void main() {
       expect(newBaggage.get('sentry-user_segment'), 'segment');
       expect(newBaggage.get('sentry-transaction'), 'name');
       expect(newBaggage.get('sentry-sample_rate'), '1');
+      expect(newBaggage.get('sentry-sampled'), 'true');
     });
 
     test('skip transaction name if low cardinality', () {
@@ -562,6 +563,7 @@ void main() {
       expect(context.userSegment, 'segment');
       expect(context.transaction, 'name');
       expect(context.sampleRate, '1');
+      expect(context.sampled, 'true');
     });
   });
 }