RequestDeviceCode will initiate the OAuth2 device authorization flow.

WaitForDeviceAuthorization polls the token URL waiting for the user to authorize the app.

ErrAccessDenied is an error returned when the user has denied this app access to their account.

Config is a version of oauth2.Config augmented with device endpoints.

A DeviceCode represents the user-visible code, verification URL and device-visible code used to allow for user authorisation of this app.

DeviceEndpoint contains the URLs required to initiate the OAuth2.0 flow for a provider's device flow.

HTTPClient defines the required http client interface.