code: public GitlabProjectMember addProjectMember(GitlabProject project, GitlabUser user, GitlabAccessLevel accessLevel) throws IOException {
          return addProjectMember(project.getId(), user.getId(), accessLevel);
      }
docs: Add a project member.
  
  @param project     the GitlabProject
  @param user        the GitlabUser
  @param accessLevel the GitlabAccessLevel
  @return the GitlabProjectMember
  @throws IOException on gitlab api call error