Message

A message sent by a user.

Attribute	Type	Description
type	string	always `message`
text	string	message content
attachments	array	a list of attachment objects (see below)

{
    "type": "message",
    "text": "hello",
    "attachments": []
}

File attachment

Attribute	Type	Description
type	string	always `file`
url	string	file URL

{
    "type": "file",
    "url": "http://example.com/file.zip"
}

Attribute	Type	Description
type	string	always `video`
url	string	video file URL

{
    "type": "video",
    "url": "http://example.com/file.mp4"
}

Attribute	Type	Description
type	string	always `image`
url	string	image file URL

{
    "type": "image",
    "url": "http://example.com/file.png"
}

Attribute	Type	Description
type	string	always `audio`
url	string	audio file URL

{
    "type": "audio",
    "url": "http://example.com/file.mp3"
}