Store user's OAUTH token in each check

[mfellner]

For certain API operations that are automatically performed by the web service in response to a webhook we need a valid OAUTH token.

The webhook events and resulting operations are always associated with a check. So it would make sense to save the current user's token in each check that gets turned on.

[prayerslayer]

Yup, just keep in mind that there might not always be a token for a check (ie after revocation).