add product and purchase

pom.xml

.../java/com/hepia/demobdd/controller/ProductController.java

...java/com/hepia/demobdd/controller/PurchaseController.java

src/main/java/com/hepia/demobdd/dto/PurchaseRequest.java

src/main/java/com/hepia/demobdd/entity/Product.java

src/main/java/com/hepia/demobdd/entity/Purchase.java

src/main/java/com/hepia/demobdd/entity/User.java

.../java/com/hepia/demobdd/repository/ProductRepository.java

...java/com/hepia/demobdd/repository/PurchaseRepository.java

src/main/resources/application.properties

src/main/resources/data.sql

src/main/resources/db/migration/V2_0__Order_table.sql

src/main/resources/db/migration/V2_1__Initial_data.sql