code: public GitlabUpload uploadFile(GitlabProject project, File file) throws IOException {
          String tailUrl = GitlabProject.URL + "/" + sanitizeProjectId(project.getId()) + GitlabUpload.URL;
          return dispatch().withAttachment("file", file).to(tailUrl, GitlabUpload.class);
      }
docs: Uploads a file to a project
  
  @param project
  @param file
  @return
  @throws IOException on gitlab api call error