fix: Count cluster messages as cluster traffic (#8308)

src/test/overlay/traffic_count_test.cpp

@@ -25,6 +25,16 @@ public:
         auto const known = TrafficCount::categorize(message, protocol::mtPING, false);
         BEAST_EXPECT(known == TrafficCount::Category::Base);
 
+        // cluster messages have a category of their own, in both directions; the same lookup
+        // serves outbound traffic, so a missing entry would hide them from a node's report
+        // whichever way they traveled
+        BEAST_EXPECT(
+            TrafficCount::categorize(message, protocol::mtCLUSTER, true) ==
+            TrafficCount::Category::Cluster);
+        BEAST_EXPECT(
+            TrafficCount::categorize(message, protocol::mtCLUSTER, false) ==
+            TrafficCount::Category::Cluster);
+
         // an unknown message type is categorized as unknown
         auto const unknown =
             TrafficCount::categorize(message, static_cast<protocol::MessageType>(99), false);

src/xrpld/overlay/detail/TrafficCount.cpp

@@ -11,6 +11,7 @@ namespace xrpl {
 std::unordered_map<protocol::MessageType, TrafficCount::Category> const kTypeLookup = {
     {protocol::mtPING, TrafficCount::Category::Base},
     {protocol::mtSTATUS_CHANGE, TrafficCount::Category::Base},
+    {protocol::mtCLUSTER, TrafficCount::Category::Cluster},
     {protocol::mtMANIFESTS, TrafficCount::Category::Manifests},
     {protocol::mtENDPOINTS, TrafficCount::Category::Overlay},
     {protocol::mtTRANSACTION, TrafficCount::Category::Transaction},