feature: Add optimistic offline lock (#1306) (#2551)

optimistic-offline-lock/src/main/java/com/iluwatar/api/UpdateService.java

@@ -0,0 +1,18 @@
+package com.iluwatar.api;
+
+/**
+ * Service for entity update.
+ *
+ * @param <T> target entity
+ */
+public interface UpdateService<T> {
+
+  /**
+   * Update entity.
+   *
+   * @param obj entity to update
+   * @param id  primary key
+   * @return modified entity
+   */
+  T doUpdate(T obj, long id);
+}