feat(UserRepository) : 임의의 DB 접근하는 Repository 객체 추가

#15

src/main/java/client/repsotiroy/UserRepository.java

@@ -0,0 +1,26 @@
+package client.repsotiroy;
+
+import client.model.User;
+import spring.mvc.annotation.Repository;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@Repository
+public class UserRepository {
+    private final Map<Long, User> temporaryDatabase = new HashMap<>();
+    private Long SEQUENCE = 0L;
+
+    public void save(final User user) {
+        temporaryDatabase.put(SEQUENCE++,user);
+    }
+
+    public List<User> getUsersWithLimit(int wannaSize) {
+        List<User> allUsers = (List<User>) temporaryDatabase.values();
+
+        return allUsers.stream()
+                .limit(wannaSize)
+                .toList();
+    }
+}