ADD file uploads testing complate

pom.xml

src/main/java/com/example/demo/TestController.java

src/main/java/com/example/demo/UserDto.java

src/main/java/com/example/demo/constant/ItemSellStatus.java

src/main/java/com/example/demo/entity/Item.java

...main/java/com/example/demo/repository/ItemRepository.java

src/main/resources/application-test.properties

src/main/resources/application.properties

src/test/java/com/example/demo/ItemRepositoryTest.java