#995: Add required feature to MinecraftExperimental for easy lookups

By: 2008Choco <hawkeboyz2@hotmail.com>

paper-api/src/main/java/org/bukkit/MinecraftExperimental.java

@@ -24,4 +24,29 @@ import org.jetbrains.annotations.ApiStatus;
 })
 @ApiStatus.Internal
 public @interface MinecraftExperimental {
+
+    /**
+     * Get the feature that must be enabled for the annotated object to be valid.
+     * <p>
+     * While this value is not used anywhere in Bukkit, it is a convenience value to assist
+     * in locating relevant annotated elements for removal once no longer deemed an experimental
+     * feature by Minecraft. See {@link Requires} for information about use in plugins.
+     *
+     * @return the required feature flag
+     */
+    Requires value();
+
+    /**
+     * An enum identifying a feature flag required by a {@link MinecraftExperimental} feature.
+     * <p>
+     * Constants defined by this enum <strong>ARE NOT API!</strong> Constants may be added or
+     * removed without warning and will not necessarily align perfectly with those defined in
+     * FeatureFlag. At no point should plugins depend on this enum. Refer to {@link FeatureFlag}
+     * instead.
+     */
+    @ApiStatus.Internal
+    public enum Requires {
+
+        UPDATE_1_21
+    }
 }