SPIGOT-4029: Add event for commands being sent to client

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/event/player/PlayerCommandSendEvent.java

@@ -0,0 +1,51 @@
+package org.bukkit.event.player;
+
+import java.util.Collection;
+import org.bukkit.Warning;
+import org.bukkit.entity.Player;
+import org.bukkit.event.HandlerList;
+
+/**
+ * This event is called when the list of available server commands is sent to
+ * the player.
+ * <br>
+ * Commands may be removed from display using this event, but implementations
+ * are not required to securely remove all traces of the command. If secure
+ * removal of commands is required, then the command should be assigned a
+ * permission which is not granted to the player.
+ *
+ * @deprecated draft API
+ */
+@Deprecated
+@Warning(false)
+public class PlayerCommandSendEvent extends PlayerEvent {
+
+    private static final HandlerList handlers = new HandlerList();
+    private final Collection<String> commands;
+
+    public PlayerCommandSendEvent(final Player player, final Collection<String> commands) {
+        super(player);
+        this.commands = commands;
+    }
+
+    /**
+     * Returns a mutable collection of all top level commands to be sent.
+     * <br>
+     * It is not legal to add entries to this collection, only remove them.
+     * Behaviour of adding entries is undefined.
+     *
+     * @return collection of all commands
+     */
+    public Collection<String> getCommands() {
+        return commands;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}