isAssignee method
Checks if a user is an assignee for the specified repository.
API docs: https://developer.github.com/v3/issues/assignees/#check-assignee
Implementation
Future<bool> isAssignee(RepositorySlug slug, String repoName) {
return github
.request('GET', '/repos/${slug.fullName}/assignees/$repoName')
.then((response) => response.statusCode == StatusCodes.NO_CONTENT);
}