Add ServerPostConnectEvent as a less confusing (and non-blocking) alternative to ServerConnectedEvent

api/src/main/java/com/velocitypowered/api/event/player/ServerPostConnectEvent.java

@@ -0,0 +1,39 @@
+package com.velocitypowered.api.event.player;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.server.RegisteredServer;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * Fired after the player has connected to a server. The server the player is now connected to is
+ * available in {@link Player#getCurrentServer()}.
+ */
+@Beta
+public class ServerPostConnectEvent {
+  private final Player player;
+  private final RegisteredServer previousServer;
+
+  public ServerPostConnectEvent(Player player,
+      @Nullable RegisteredServer previousServer) {
+    this.player = Preconditions.checkNotNull(player, "player");
+    this.previousServer = previousServer;
+  }
+
+  public Player getPlayer() {
+    return player;
+  }
+
+  public @Nullable RegisteredServer getPreviousServer() {
+    return previousServer;
+  }
+
+  @Override
+  public String toString() {
+    return "ServerPostConnectEvent{"
+        + "player=" + player
+        + ", previousServer=" + previousServer
+        + '}';
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/TransitionSessionHandler.java

@@ -4,6 +4,7 @@ import static com.velocitypowered.proxy.connection.backend.BackendConnectionPhas
 import static com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeHandshakeBackendPhase.HELLO;
 
 import com.velocitypowered.api.event.player.ServerConnectedEvent;
+import com.velocitypowered.api.event.player.ServerPostConnectEvent;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.ConnectionTypes;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
@@ -113,6 +114,8 @@ public class TransitionSessionHandler implements MinecraftSessionHandler {
           serverConn.getPlayer().setConnectedServer(serverConn);
 
           // We're done! :)
+          server.getEventManager().fireAndForget(new ServerPostConnectEvent(serverConn.getPlayer(),
+              existingConnection == null ? null : existingConnection.getServer()));
           resultFuture.complete(ConnectionRequestResults.successful(serverConn.getServer()));
         }, smc.eventLoop())
         .exceptionally(exc -> {