#3736: Add simple login payload API

api/src/main/java/net/md_5/bungee/api/connection/PendingConnection.java

@@ -113,4 +113,18 @@ public interface PendingConnection extends Connection
      */
     @ApiStatus.Experimental
     CompletableFuture<byte[]> retrieveCookie(String cookie);
+
+    /**
+     * Sends a login payload request to the client.
+     *
+     * @param channel the channel to send this data via
+     * @param data the data to send
+     * @return a {@link CompletableFuture} that will be completed when the Login
+     * Payload response is received. If the Vanilla client doesn't know the
+     * channel, the {@link CompletableFuture} will complete with a null value
+     * @throws IllegalStateException if the player's version is not at least
+     * 1.13
+     */
+    @ApiStatus.Experimental
+    CompletableFuture<byte[]> sendData(String channel, byte[] data);
 }