Alerts processed for unlicensed users

[mcoles]

VizAlerts will still attempt to process an alert based on an Unlicensed user who is still subscribed to a view on an Alerts schedule. This causes a failure email to be sent, because Tableau Server will refuse to provide the CSV data for a view on behalf of an unlicensed user.

My thought is that the correct behavior should be the same as standard Subscriptions functionality, which is that any Subscriptions for an unlicensed user are simply ignored. We could just exclude that data in the SQL query in the config file, but it'd be better to set a flag for those rows then have VizAlerts skip them but log that it did so. That way there's more visibility for the Admin on what's going on.

[mcoles]

Improved this behavior such that now, if an alert is slated to be tested when the subscriber is unlicensed in Tableau Server, the alert will be skipped, but an email will be sent to the admin / subscriber with a clear reason for the error.