Add trace token to query events

Author: dain

presto-main/src/main/java/io/prestosql/event/QueryMonitor.java

@@ -234,6 +234,7 @@ private QueryContext createQueryContext(SessionRepresentation session, Optional<
         return new QueryContext(
                 session.getUser(),
                 session.getPrincipal(),
+                session.getTraceToken(),
                 session.getRemoteUserAddress(),
                 session.getUserAgent(),
                 session.getClientInfo(),

presto-spi/src/main/java/io/prestosql/spi/eventlistener/QueryContext.java

@@ -27,6 +27,7 @@ public class QueryContext
 {
     private final String user;
     private final Optional<String> principal;
+    private final Optional<String> traceToken;
     private final Optional<String> remoteClientAddress;
     private final Optional<String> userAgent;
     private final Optional<String> clientInfo;
@@ -49,6 +50,7 @@ public class QueryContext
     public QueryContext(
             String user,
             Optional<String> principal,
+            Optional<String> traceToken,
             Optional<String> remoteClientAddress,
             Optional<String> userAgent,
             Optional<String> clientInfo,
@@ -66,6 +68,7 @@ public QueryContext(
     {
         this.user = requireNonNull(user, "user is null");
         this.principal = requireNonNull(principal, "principal is null");
+        this.traceToken = requireNonNull(traceToken, "traceToken is null");
         this.remoteClientAddress = requireNonNull(remoteClientAddress, "remoteClientAddress is null");
         this.userAgent = requireNonNull(userAgent, "userAgent is null");
         this.clientInfo = requireNonNull(clientInfo, "clientInfo is null");
@@ -94,6 +97,12 @@ public Optional<String> getPrincipal()
         return principal;
     }
 
+    @JsonProperty
+    public Optional<String> getTraceToken()
+    {
+        return traceToken;
+    }
+
     @JsonProperty
     public Optional<String> getRemoteClientAddress()
     {