Graph token is missing from repo details API call

[drazisil-codecov]

With the change to v2, customer no longer have a way to fetch the graph token.

It should be at this endpoint https://docs.codecov.com/reference/repos_config_retrieve

It was formerly available via https://codecov.io/api/pub/<PROVIDER>/<OWNER>/<REPO>/settings

[thebjorn]

Concretely, we need the graph token to show the codecov badge in the readme

.. image:: https://codecov.io/gl/norsktest/tt3/branch/master/graph/badge.svg?token=<graph-token>
  :target: https://codecov.io/gl/norsktest/tt3

We auto-generate the readme file when creating a new project and we need an api to fetch the <graph-token> since it is unique per repo. A solution where we could use a common token for all our repos would also solve our problems.