3.6-beta

add force rankup and prestige
add update notification on join
more reliable legacy server version check

added permissions: rankup.admin (grants rankup.checkversion, rankup.reload, rankup.force, and rankup.notify), rankup.notify (receive update notiifications on login), rankup.force (force a player to rankup or prestige)

src/main/java/sh/okx/rankup/util/ItemUtil.java

@@ -0,0 +1,31 @@
+package sh.okx.rankup.util;
+
+import com.google.common.base.Suppliers;
+import java.util.function.Supplier;
+import org.bukkit.Material;
+
+public class ItemUtil {
+  private static Supplier<Boolean> flattenedSupplier = Suppliers.memoize(ItemUtil::isServerFlattenedPrivate);
+
+  private static boolean isServerFlattenedPrivate() {
+    try {
+      Material.valueOf("BLACK_STAINED_GLASS_PANE");
+      return true;
+    } catch (IllegalArgumentException e) {
+      return false;
+    }
+  }
+
+  /**
+   * Determines if a server is post-flattening or pre-flattening.
+   * The flattening is the name for a process where, instead of using durability to represent
+   * similar items, Mojang decided to use distinct item types for each item.
+   * This caused many {@link Material} names to change, making some things incompatible.
+   * The flattening happened in 1.13.
+   *
+   * @return true if the server is post-flattening (server versions 1.13, 1.14, 1.15) or false if it is pre-flattening (1.12, 1.11, 1.10 etc)
+   */
+  public static boolean isServerFlattened() {
+    return flattenedSupplier.get();
+  }
+}