code: public GitlabNote addDiscussionNote(GitlabMergeRequest mergeRequest,
              int discussionId, String body) throws IOException {
          String tailUrl = GitlabProject.URL + "/" + mergeRequest.getProjectId() +
                  GitlabMergeRequest.URL + "/" + mergeRequest.getIid() +
                  GitlabDiscussion.URL + "/" + discussionId +
                  GitlabNote.URL;
          return dispatch().with("body", body).to(tailUrl, GitlabNote.class);
      }
docs: Add a note to existing merge request discussion.
  
  @param mergeRequest  The merge request of the discussion.
  @param discussionId  The id of the discussion to add a note to.
  @param body          The content of the discussion.
  
  @return The added note object.
  @throws IOException on a GitLab api call error