remove follow

src/main/java/io/spring/infrastructure/user/MyBatisUserRepository.java

@@ -43,11 +43,18 @@ public class MyBatisUserRepository implements UserRepository {
 
     @Override
     public void saveRelation(FollowRelation followRelation) {
-        userMapper.saveRelation(followRelation);
+        if (!findRelation(followRelation.getUserId(), followRelation.getTargetId()).isPresent()) {
+            userMapper.saveRelation(followRelation);
+        }
     }
 
     @Override
     public Optional<FollowRelation> findRelation(String userId, String targetId) {
         return Optional.ofNullable(userMapper.findRelation(userId, targetId));
     }
+
+    @Override
+    public void removeRelation(FollowRelation followRelation) {
+        userMapper.deleteRelation(followRelation);
+    }
 }

src/main/java/io/spring/infrastructure/user/UserMapper.java

@@ -21,4 +21,6 @@ public interface UserMapper {
     FollowRelation findRelation(@Param("userId") String userId, @Param("targetId") String targetId);
 
     void saveRelation(@Param("followRelation") FollowRelation followRelation);
+
+    void deleteRelation(@Param("followRelation") FollowRelation followRelation);
 }