Use Paper API for detecting proxies (1.21.6+)

Related #1312

Author: TuxCoding

bukkit/pom.xml

@@ -168,7 +168,7 @@
         <dependency>
             <groupId>io.papermc.paper</groupId>
             <artifactId>paper-api</artifactId>
-            <version>1.20.6-R0.1-SNAPSHOT</version>
+            <version>1.21.6-R0.1-SNAPSHOT</version>
             <scope>provided</scope>
             <!-- Use our own newer api version -->
             <exclusions>

bukkit/src/main/java/com/github/games647/fastlogin/bukkit/BungeeManager.java

@@ -31,6 +31,7 @@
 import com.github.games647.fastlogin.core.message.NamespaceKey;
 import com.google.common.io.ByteArrayDataOutput;
 import com.google.common.io.ByteStreams;
+import io.papermc.paper.configuration.ServerConfiguration;
 import org.bukkit.Bukkit;
 import org.bukkit.Server;
 import org.bukkit.entity.Player;
@@ -133,6 +134,13 @@ private boolean isVelocityEnabled()
     }
 
     private boolean detectProxy() {
+        try {
+            ServerConfiguration.class.getDeclaredMethod("isProxyEnabled");
+            return Bukkit.getServerConfig().isProxyEnabled();
+        } catch (NoSuchMethodException noSuchMethodEx) {
+            // Ignore continue below
+        }
+
         try {
             if (isProxySupported("org.spigotmc.SpigotConfig", "bungee")) {
                 return true;