This allows operators to permit access to Chronograf only to users belonging
to a set of specific Heroku organizations. This is controlled using the
HEROKU_ORGS env or the --heroku-organizations switch.
This adds an Oauth2 Provider for authenticating users against Heroku's
API. In contrast to other Providers, a maintained client library for
interacting with the Heroku API was not available, so direct HTTP calls
are made instead. This follows with their documentation posted here:
https://devcenter.heroku.com/articles/oauth2-heroku-go
Michael Desa
Chris Goller
Tim Raymond