code: public void unblockUser(Integer targetUserId) throws IOException {
  
          String tailUrl = GitlabUser.USERS_URL + "/" + targetUserId + GitlabUser.UNBLOCK_URL;
  
          retrieve().method(POST).to(tailUrl, Void.class);
      }
docs: Unblock a user
  
  @param targetUserId The id of the Gitlab user
  @throws IOException on gitlab api call error