Add PrepareResultEvent / PrepareGrindstoneEvent

Adds a new event for all crafting stations that generate a result slot item

Anvil, Grindstone and Smithing now extend this event

Grindstone is a backwards compat from a previous PrepareGrindstoneEvent

paper-api/src/main/java/com/destroystokyo/paper/event/inventory/PrepareGrindstoneEvent.java

@@ -0,0 +1,31 @@
+package com.destroystokyo.paper.event.inventory;
+
+import org.bukkit.Warning;
+import org.bukkit.inventory.GrindstoneInventory;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Called when an item is put in a slot for grinding in a Grindstone
+ *
+ * @deprecated use {@link org.bukkit.event.inventory.PrepareGrindstoneEvent}
+ */
+@Deprecated(since = "1.16.1")
+@Warning
+public class PrepareGrindstoneEvent extends PrepareResultEvent {
+
+    @ApiStatus.Internal
+    public PrepareGrindstoneEvent(@NotNull InventoryView inventory, @Nullable ItemStack result) {
+        super(inventory, result);
+    }
+
+    @NotNull
+    @Override
+    public GrindstoneInventory getInventory() {
+        return (GrindstoneInventory) super.getInventory();
+    }
+
+}

paper-api/src/main/java/com/destroystokyo/paper/event/inventory/PrepareResultEvent.java

@@ -0,0 +1,42 @@
+package com.destroystokyo.paper.event.inventory;
+
+import org.bukkit.event.inventory.PrepareInventoryResultEvent;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Called when an item is put in an inventory containing a result slot
+ */
+@NullMarked
+public class PrepareResultEvent extends PrepareInventoryResultEvent {
+
+    // HandlerList on PrepareInventoryResultEvent to ensure api compat
+
+    @ApiStatus.Internal
+    public PrepareResultEvent(final InventoryView inventory, final @Nullable ItemStack result) {
+        super(inventory, result);
+    }
+
+    /**
+     * Get result item, may be {@code null}.
+     *
+     * @return result item
+     */
+    @Override
+    public @Nullable ItemStack getResult() {
+        return super.getResult();
+    }
+
+    /**
+     * Set result item, may be {@code null}.
+     *
+     * @param result result item
+     */
+    @Override
+    public void setResult(final @Nullable ItemStack result) {
+        super.setResult(result);
+    }
+}