Deprecate all the API classes that will be removed in Floodgate 3.0

See #536 for more information

api/src/main/java/org/geysermc/floodgate/api/InstanceHolder.java

@@ -38,9 +38,9 @@ public final class InstanceHolder {
     @Getter private static PlayerLink playerLink;
     @Getter private static FloodgateEventBus eventBus;
 
-    @Getter private static PlatformInjector injector;
-    @Getter private static PacketHandlers packetHandlers;
-    @Getter private static HandshakeHandlers handshakeHandlers;
+    private static PlatformInjector injector;
+    private static PacketHandlers packetHandlers;
+    private static HandshakeHandlers handshakeHandlers;
     private static UUID storedKey;
 
     public static boolean set(
@@ -68,4 +68,31 @@ public final class InstanceHolder {
         InstanceHolder.handshakeHandlers = handshakeHandlers;
         return true;
     }
+
+    /**
+     * @deprecated Injector addons will be removed with the launch of Floodgate 3.0. Please look at
+     * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
+     */
+    @Deprecated
+    public static PlatformInjector getInjector() {
+        return InstanceHolder.injector;
+    }
+
+    /**
+     * @deprecated Packet handlers will be removed with the launch of Floodgate 3.0. Please look at
+     * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
+     */
+    @Deprecated
+    public static PacketHandlers getPacketHandlers() {
+        return InstanceHolder.packetHandlers;
+    }
+
+    /**
+     * @deprecated Handshake handlers will be removed with the launch of Floodgate 3.0. Please look at
+     * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
+     */
+    @Deprecated
+    public static HandshakeHandlers getHandshakeHandlers() {
+        return InstanceHolder.handshakeHandlers;
+    }
 }

api/src/main/java/org/geysermc/floodgate/api/handshake/HandshakeData.java

@@ -31,11 +31,8 @@ import org.geysermc.floodgate.util.BedrockData;
 import org.geysermc.floodgate.util.LinkedPlayer;
 
 /**
- * For advanced users only! You shouldn't play with this unless you know what you're doing.<br>
- * <br>
- * This class allows you change specific things of a Bedrock player before it is applied to the
- * server. Note that at the time I'm writing this that the HandshakeData is created after requesting
- * the player link. So the link is present here, if applicable.
+ * @deprecated Handshake handlers will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
  */
 @Deprecated
 public interface HandshakeData {

api/src/main/java/org/geysermc/floodgate/api/handshake/HandshakeHandler.java

@@ -26,13 +26,8 @@
 package org.geysermc.floodgate.api.handshake;
 
 /**
- * This class allows you to change and/or get specific data of the Bedrock client before Floodgate
- * does something with this data. This means that Floodgate decrypts the data, then calls the
- * handshake handlers and then applies the data to the connection.<br>
- * <br>
- * /!\ Note that this class will be called for both Java and Bedrock connections, but {@link
- * HandshakeData#isFloodgatePlayer()} will be false and Floodgate related methods will return null
- * for Java players
+ * @deprecated Handshake handlers will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
  */
 @Deprecated
 @FunctionalInterface

api/src/main/java/org/geysermc/floodgate/api/handshake/HandshakeHandlers.java

@@ -26,10 +26,8 @@
 package org.geysermc.floodgate.api.handshake;
 
 /**
- * @deprecated This system has been deprecated and will not be available in the new API that will be
- * introduced when Geyser will include Floodgate (and thus will have some common base API).
- * <br>
- * It might be replaced with an event (probably internal), but that isn't certain yet.
+ * @deprecated Handshake handlers will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
  */
 @Deprecated
 public interface HandshakeHandlers {

api/src/main/java/org/geysermc/floodgate/api/inject/InjectorAddon.java

@@ -27,6 +27,11 @@ package org.geysermc.floodgate.api.inject;
 
 import io.netty.channel.Channel;
 
+/**
+ * @deprecated Injector addons will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
+ */
+@Deprecated
 public interface InjectorAddon {
     /**
      * Called when injecting a specific channel (every client that is connected to the server has

api/src/main/java/org/geysermc/floodgate/api/inject/PlatformInjector.java

@@ -26,12 +26,10 @@
 package org.geysermc.floodgate.api.inject;
 
 /**
- * The global interface of all the Platform Injectors. The injector can be used for various things.
- * It is used internally for getting Floodgate data out of the handshake packet and for debug mode,
- * but there is also an option to add your own addons. Note that every Floodgate platform that
- * supports netty should implement this, but the platform implementation isn't required to implement
- * this.
+ * @deprecated Injector addons will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
  */
+@Deprecated
 public interface PlatformInjector {
     /**
      * Injects the server connection. This will allow various addons (like getting the Floodgate

api/src/main/java/org/geysermc/floodgate/api/packet/PacketHandler.java

@@ -28,8 +28,10 @@ package org.geysermc.floodgate.api.packet;
 import io.netty.channel.ChannelHandlerContext;
 
 /**
- * For advanced users only! You shouldn't play with this unless you know what you're doing.
+ * @deprecated Packet handlers will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
  */
+@Deprecated
 public interface PacketHandler {
     /**
      * Called when a registered packet has been seen.

api/src/main/java/org/geysermc/floodgate/api/packet/PacketHandlers.java

@@ -28,6 +28,11 @@ package org.geysermc.floodgate.api.packet;
 import io.netty.channel.ChannelHandlerContext;
 import org.geysermc.floodgate.api.util.TriFunction;
 
+/**
+ * @deprecated Packet handlers will be removed with the launch of Floodgate 3.0. Please look at
+ * <a href="https://github.com/GeyserMC/Floodgate/issues/536">#536</a> for additional context.
+ */
+@Deprecated
 public interface PacketHandlers {
     /**
      * Register a specific class for a specific consumer.