Expose Messages as SMS in APi

Currently, the reservation message object does not expose if the message was received via SMS, email of the booking platform. This results in 3rd party message providers such as AI bots not being able to tell when a message was sent via SMS, and therefore they cannot respond via SMS.

This results in guests messaging me via SMS and my AI bot responding to them via Airbnb, booking.com, VRBO or email. As you can imagine, this confuses guests or worse they don't know I've even responded to them. I end up having to come in all day and copy paste my AI bot's response to SMS. What's worse, is because it is SMS, I have to cut up the response in to 140 character chunks and send them out. This results in more work for me than if I just didn't use an AI auto-responder.