Add Configuration State API (#1261)

* Implement Configuration State events

* Implement PlayerFinishedConfigurationEvent

* Fixed PlayerFinishConfigurationEvent execution

* Apply suggestions

* Fix keep alive when blocking PlayerFinishConfigurationEvent

* Add ServerConnection to configuration events

* Separate PlayPacketQueueHandler to fix AutoReadHolderHandler

---------

Co-authored-by: Gero <gecam59@gmail.com>

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerEnterConfigurationEvent.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.network.ProtocolState;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is executed when a player with version 1.20.2 or higher enters the configuration phase.
+ * <p>From this moment on, until the {@link PlayerFinishedConfigurationEvent} is executed,
+ * the {@linkplain Player#getProtocolState()} method is guaranteed
+ * to return {@link ProtocolState#CONFIGURATION}.</p>
+ *
+ * @param player The player that has entered the configuration phase.
+ * @param server The server that will now (re-)configure the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+public record PlayerEnterConfigurationEvent(@NotNull Player player, ServerConnection server) {
+}

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerFinishConfigurationEvent.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.event.annotation.AwaitingEvent;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is executed when the player is about to finish the Configuration state.
+ * <p>Velocity will wait for this event to finish the configuration phase on the client.</p>
+ *
+ * @param player The player who is about to complete the configuration phase.
+ * @param server The server that is currently (re-)configuring the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+@AwaitingEvent
+public record PlayerFinishConfigurationEvent(@NotNull Player player, @NotNull ServerConnection server) {
+}

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerFinishedConfigurationEvent.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.network.ProtocolState;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Event executed when a player of version 1.20.2 or higher finishes the Configuration state.
+ * <p>From this moment on, the {@link Player#getProtocolState()} method
+ * will return {@link ProtocolState#PLAY}.</p>
+ *
+ * @param player The player who has completed the Configuration state
+ * @param server The server that has (re-)configured the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+public record PlayerFinishedConfigurationEvent(@NotNull Player player, @NotNull ServerConnection server) {
+}