Support pagination without totalItems requirement
To support GitHub import pagination (https://gitlab.com/gitlab-org/gitlab-ce/issues/59060), we need a way to paginate without needing to know the totalItems
of the list (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26512). The API gives back a previous and next link, and the number of page numbers can be calculated form that link. However, to get the exact number of items in the list, you would have make two separate API calls to get this information each time (https://github.com/octokit/octokit.rb/issues/787#issuecomment-313529680). That's not ideal.
In addition, to support keyset pagination for PostgreSQL (https://gitlab.com/gitlab-org/gitlab-ce/issues/45756), we don't even know the total number of pages: we only know if there's a next or previous page.
/cc: @lbennett, @timzallmann