added sample rule to beginSegmentWithSampling (#204)

Author: willarmiros

aws-xray-recorder-sdk-core/src/main/java/com/amazonaws/xray/AWSXRayRecorder.java

@@ -405,7 +405,12 @@ public Segment beginSegmentWithSampling(String name) {
         final SamplingRequest samplingRequest = new SamplingRequest(name, null, null, null, this.origin);
         final SamplingResponse samplingResponse = this.getSamplingStrategy().shouldTrace(samplingRequest);
         if (samplingResponse.isSampled()) {
-            return beginSegment(name);
+            Segment segment = beginSegment(name);
+            if (samplingResponse.getRuleName().isPresent()) {
+                segment.setRuleName(samplingResponse.getRuleName().get());
+            }
+
+            return segment;
         }
 
         return beginNoOpSegment();

aws-xray-recorder-sdk-core/src/test/java/com/amazonaws/xray/AWSXRayRecorderTest.java

@@ -855,6 +855,8 @@ public void testBeginSegmentWithSamplingDoesSample() {
 
         Segment segment = AWSXRay.beginSegmentWithSampling("test");
         assertThat(segment.isSampled()).isTrue();
+        assertThat(segment.getAws().get("xray")).isInstanceOfSatisfying(
+            Map.class, xray -> assertThat(xray.get("rule_name")).isEqualTo("rule"));
     }
 
     @Test