code: public GitlabMilestone createMilestone(
              Serializable projectId,
              GitlabMilestone milestone) throws IOException {
          String title = milestone.getTitle();
          String description = milestone.getDescription();
          Date dateDue = milestone.getDueDate();
          Date dateStart = milestone.getStartDate();
          return createMilestone(projectId, title, description, dateDue, dateStart);
      }
docs: Creates a new project milestone.
  
  @param projectId The ID of the project.
  @param milestone The milestone to create.
  @return The newly created, de-serialized milestone.
  @throws IOException on gitlab api call error