title: How can one use Binder (mybinder.org) with private Github repositories?
body: <p>After reviewing this exact issue (<a href="https://github.com/jupyterhub/binderhub/issues/237" rel="noreferrer">https://github.com/jupyterhub/binderhub/issues/237</a>) it seems that the functionality for this has been implemented with this merged pull request (<a href="https://github.com/jupyterhub/binderhub/pull/671" rel="noreferrer">https://github.com/jupyterhub/binderhub/pull/671</a>).</p>
  
  <p>However I can not seem to find guidance in the docs or elsewhere which explains what should go into the <code>secrets.yml</code> file or if there are other steps required in order to use Binder with private Github repos (Apologies if I have missed the obvious -- complete Binder noobie here)</p>
  
  <p>Link to my same question in the original issue: <a href="https://github.com/jupyterhub/binderhub/issues/237#issuecomment-462711995" rel="noreferrer">https://github.com/jupyterhub/binderhub/issues/237#issuecomment-462711995</a></p>