add draft inferred proxy spans as http request parent

Author: jordan-wong

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java

@@ -0,0 +1,10 @@
+diff a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java	(rejected hunks)
+@@ -150,7 +523,7 @@ public abstract class HttpServerDecorator<REQUEST, CONNECTION, RESPONSE, REQUEST
+     if (null != carrier && null != getter) {
+       tracer().getDataStreamsMonitoring().setCheckpoint(span, SERVER_PATHWAY_EDGE_TAGS, 0, 0);
+     }
+-    return span;
++    return new MySpan(apiGtwSpan, span);
+   }
+ 
+   public AgentSpan onRequest(

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java.rej

@@ -18,6 +18,8 @@ public enum TracePropagationStyle {
   // Amazon X-Ray context propagation style
   // https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-tracingheader
   XRAY,
+  // TODO: add INFERREDPROXY style here,
+  // may NOT make full sense to add, because they are meeant to be for
   // W3C trace context propagation style
   // https://www.w3.org/TR/trace-context-1/
   TRACECONTEXT,

dd-trace-api/src/main/java/datadog/trace/api/TracePropagationStyle.java

@@ -159,6 +159,7 @@ public static Extractor createExtractor(
         case TRACECONTEXT:
           extractors.add(W3CHttpCodec.newExtractor(config, traceConfigSupplier));
           break;
+          // TODO: make case INFERREDPROXYSPAN
         default:
           log.debug("No implementation found to extract propagation style: {}", style);
           break;