Put is_crash_ping in the payload

Author: amarziali

dd-java-agent/agent-crashtracking/src/main/java/datadog/crashtracking/CrashUploader.java

@@ -120,6 +120,7 @@ public void notifyCrashStarted(String error) {
       writer.name("crash_uuid").value(storedConfig.reportUUID);
       writer.name("kind").value("Crash ping");
       writer.name("current_schema_version").value("1.0");
+      writer.name("is_crash_ping").value(true);
       writer
           .name("message")
           .value(

dd-java-agent/agent-crashtracking/src/test/resources/golden/sample-ping-for-telemetry.txt

@@ -1 +1 @@
-{"crash_uuid":"a4194cd6-8cb3-45fd-9bd9-3af83e0a3ad3","kind":"Crash ping","current_schema_version":"1.0","message":"Crashtracker crash ping: crash processing started"}
+{"crash_uuid":"a4194cd6-8cb3-45fd-9bd9-3af83e0a3ad3","kind":"Crash ping","current_schema_version":"1.0","is_crash_ping":true,"message":"Crashtracker crash ping: crash processing started"}