Make a call to this endpoint to unsubscribe a user from a subscription type or channel. If no subscriptions
are present in the request, the user is unsubscribed from all subscriptions. If subscriptions are present
in the request, the user is unsubscribed from the requested type or channel combination. By default, if a
subscription exists, but the user is already unsubscribed, it records the attempt to unsubscribe the
subscription again. For TEXT subscriptions, a message is sent to the person indicating that they are
unsubscribed.

For the user object, the email data point determines which email subscriptions a user has and the phone data point
determines which text (or sms) subscriptions a user has. Passing in an email does not locate, nor unsubscribe,
a user from any sms subscriptions. Similarly, passing in a phone does not locate, nor unsubscribe, a user from any email subscriptions.