listAssignees method
Lists all available assignees (owners and collaborators) to which issues may be assigned.
API docs: https://developer.github.com/v3/issues/assignees/#list-assignees
Implementation
Stream<User> listAssignees(RepositorySlug slug) {
return PaginationHelper(github).objects('GET',
'/repos/${slug.fullName}/assignees', (dynamic i) => User.fromJson(i));
}