WebhookJsonConverter missing fields

[andrewchilcott]

The KnownProperties list is missing some known properties. This results in them being added both as fields in the event class and as unique properties. The full list of known properties should be:

private static readonly string[] KnownProperties = {"sg_event_id", "sg_message_id", "smtp-id", "event", "email", "category", "timestamp", "ip", "useragent", "type", "reason", "status", "url", "url_offset", "send_at", "tls", "cert_err", "asm_group_id", "response", "attempts" };

In the processed-with-send-at.json test data a field for asm_group_id is included but ProcessedEvent does not have a GroupId property so it is turning up in UniqueProperties. GroupId should be added to the ProcessedEvent class.

Edit:
I've just also noticed that the test data for both the click event and the delivery event also have asm_group_id but neither of the events has a GroupId property