Facebook Messenger Activity & Buttons template

[killix]

Quick Reply & Simple message buttons

The idea is to add the support of buttons with simple message

To do that, we need to identify the kind of Link (older Buttons) in AS2 send by the developers. I added the notion of new mediaType 'text/plain' to identify the quick reply behavior.

If it's accepted, we need to update all integrations with this new way and publish as breaking change.

Sender Actions

This PR added also the support of sender actions

Turn typing indicators on can be done with new Activity Object:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Create",
  "generator": {
    "id": "f6e92eb6-f69e-4eae-8158-06613461cf3a",
    "type": "Service",
    "name": "messenger"
  },
  "object": {
    "type": "Activity",
    "content": "typing/on",
  },
  "to": {
    "type": "Person",
    "id": "1396343657196792"
  }
}