User invitation token

$invitation.Email - string - Email of the person being invited.
$invitation.DateInvited - DateTime - Date the invitation was made.
$invitation.Message - string - Message sent to the invitee
$invitation.InvitationKey - Guid - Unique key representing this invitation.
$invitation.Group - Group - Group the invitation is to (if applicable).
$invitation.Section - Section - Section the invitation is to (if applicable).