Add config for the metrics/stats id until there is a good way to read it

src/main/java/de/themoep/snap/Snap.java

@@ -54,6 +54,10 @@ public Snap(ProxyServer proxy, Logger logger, @DataDirectory Path dataFolder) {
     @Subscribe
     public void onProxyInitialization(ProxyInitializeEvent event) throws NoSuchMethodException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InvocationTargetException, IOException {
         if (loadConfig()) {
+            if (!config.has("stats-id") || config.getString("stats-id").isEmpty()) {
+                config.set("stats-id", UUID.randomUUID().toString());
+                config.save();
+            }
             bungeeAdapter = new SnapBungeeAdapter(this);
             bungeeAdapter.registerEvents();
             bungeeAdapter.loadPlugins();
@@ -77,6 +81,10 @@ private boolean loadConfig() {
         return false;
     }
 
+    public PluginConfig getConfig() {
+        return config;
+    }
+
     public ProxyServer getProxy() {
         return proxy;
     }

src/main/java/de/themoep/snap/forwarding/SnapProxyServer.java

@@ -62,6 +62,7 @@
 public class SnapProxyServer extends ProxyServer {
     private final Snap snap;
 
+    private String statsId;
     private Field fIdentifierMap;
     private Set<String> channels = new HashSet<>();
     private final ListenerInfo listener;
@@ -73,6 +74,11 @@ public SnapProxyServer(Snap snap) {
         this.snap = snap;
         com.velocitypowered.api.proxy.config.ProxyConfig config = snap.getProxy().getConfiguration();
 
+        statsId = snap.getConfig().getString("stats-id");
+        if (statsId == null) {
+            statsId = UUID.randomUUID().toString();
+        }
+
         listener = new ListenerInfo(
                 snap.getProxy().getBoundAddress(),
                 LegacyComponentSerializer.legacySection().serialize(config.getMotd()),
@@ -356,7 +362,7 @@ public int getTimeout() {
 
             @Override
             public String getUuid() {
-                return UUID.randomUUID().toString();
+                return statsId;
             }
 
             @Override

src/main/resources/snap.conf

@@ -1,3 +1,6 @@
 # Whether to throw exceptions when accessing methods that aren't supported
 # Setting this to false makes them return sensible values but they might not be correct
-throw-unsupported-exception = true
+throw-unsupported-exception = true
+
+# The stats/metrics ID of this proxy, ideally the same as in the velocity.toml
+stats-id = ""