Expose client protocol version and virtual host

Add a NetworkClient interface that provides access to:
  - The socket address
  - The protocol version
  - The virtual host (the hostname/port the client used to connect
    to the server)

paper-api/src/main/java/com/destroystokyo/paper/network/NetworkClient.java

@@ -0,0 +1,39 @@
+package com.destroystokyo.paper.network;
+
+import java.net.InetSocketAddress;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Represents a client connected to the server.
+ */
+@NullMarked
+public interface NetworkClient {
+
+    /**
+     * Returns the socket address of the client.
+     *
+     * @return The client's socket address
+     */
+    InetSocketAddress getAddress();
+
+    /**
+     * Returns the protocol version of the client.
+     *
+     * @return The client's protocol version, or {@code -1} if unknown
+     * @see <a href="http://wiki.vg/Protocol_version_numbers">List of protocol
+     *     version numbers</a>
+     */
+    int getProtocolVersion();
+
+    /**
+     * Returns the virtual host the client is connected to.
+     *
+     * <p>The virtual host refers to the hostname/port the client used to
+     * connect to the server.</p>
+     *
+     * @return The client's virtual host, or {@code null} if unknown
+     */
+    @Nullable InetSocketAddress getVirtualHost();
+
+}

paper-api/src/main/java/org/bukkit/entity/Player.java

@@ -58,7 +58,7 @@ import org.jetbrains.annotations.Nullable;
 /**
  * Represents a player, connected or not
  */
-public interface Player extends HumanEntity, Conversable, OfflinePlayer, PluginMessageRecipient, net.kyori.adventure.identity.Identified, net.kyori.adventure.bossbar.BossBarViewer { // Paper
+public interface Player extends HumanEntity, Conversable, OfflinePlayer, PluginMessageRecipient, net.kyori.adventure.identity.Identified, net.kyori.adventure.bossbar.BossBarViewer, com.destroystokyo.paper.network.NetworkClient { // Paper
 
     // Paper start
     @Override