Start category usecase

2-Application/src/main/java/category/CategoryIdGenerator.java

@@ -0,0 +1,6 @@
+package category;
+
+public interface CategoryIdGenerator
+{
+	CategoryId generateId();
+}

2-Application/src/main/java/category/CategoryUseCase.java

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+package category;
+
+import java.util.Set;
+
+public class CategoryUseCase {
+
+	private final CategoryRepository categoryRepository;
+	private final CategoryIdGenerator categoryIdGenerator;
+
+	CategoryUseCase(final CategoryRepository categoryRepository, final CategoryIdGenerator idGenerator) {
+		this.categoryRepository = categoryRepository;
+		this.categoryIdGenerator = idGenerator;
+	}
+
+	public void addCategory(CategoryName name) {
+
+		var id = this.categoryIdGenerator.generateId();
+		this.categoryRepository.add(new Category(name, id));
+	}
+
+	public Set<Category> getCategories() {
+		return categoryRepository.getAll();
+	}
+}