fix: Add GenerationType and Transactional annotations (#59)

Add missing annotations required for the examples to work properly:
- `@GeneratedValue(strategy = GenerationType.IDENTITY)` for auto-incremental id
- `@Transactional` for the `DELETE` endpoint to work

Author: cchacin

modules/ROOT/pages/chapter03/chapter03.adoc

@@ -140,6 +140,7 @@ package io.microprofile.tutorial.store.product.entity;
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
 import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
 import jakarta.validation.constraints.NotNull;
 
 @Entity
@@ -152,7 +153,7 @@ import jakarta.validation.constraints.NotNull;
 public class Product {
 
     @Id
-    @GeneratedValue
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
 
     @NotNull
@@ -471,6 +472,7 @@ $ curl http://localhost:9080/mp-ecomm-store/api/products
 [source, java]
 ----
 @DELETE
+@Transactional
 @Path("products/{id}")
 public Response deleteProduct(@PathParam("id") Long id) {
      // Delete a product