fix: improves ActionEnum documentation

Fix #594

[changelog]

Author: Ant-hem

algoliasearch-core/src/main/java/com/algolia/search/models/indexing/ActionEnum.java

@@ -6,11 +6,40 @@
  * @see <a href="https://www.algolia.com/doc/api-reference/api-methods/batc">Algolia.com</a>
  */
 public class ActionEnum {
+
+  /** Add an object. Equivalent to Add an object without ID. */
   public static final String ADD_OBJECT = "addObject";
+
+  /**
+   * Add or replace an existing object. You must set the <code>objectID</code> attribute to indicate
+   * the object to update. Equivalent to Add/update an object by ID.
+   */
   public static final String UPDATE_OBJECT = "updateObject";
+
+  /**
+   * Partially update an object. You must set the <code>objectID</code> attribute to indicate the
+   * object to update. Equivalent to Partially update an object.
+   */
   public static final String PARTIAL_UPDATE_OBJECT = "partialUpdateObject";
+
+  /**
+   * Same as partialUpdateObject, except that the object is not created if the object designated by
+   * <code>objectID</code> does not exist.
+   */
   public static final String PARTIAL_UPDATE_OBJECT_NO_CREATE = "partialUpdateObjectNoCreate";
+
+  /**
+   * Delete an object. You must set the <code>objectID</code> attribute to indicate the object to
+   * delete. Equivalent to Delete an object.
+   */
   public static final String DELETE_OBJECT = "deleteObject";
+
+  /** Delete the index. Equivalent to Delete an index. */
   public static final String DELETE = "delete";
+
+  /**
+   * Remove the index’s content, but keep settings and index-specific API keys untouched. Equivalent
+   * to Clear objects.
+   */
   public static final String CLEAR = "clear";
 }