A message was sent to a channel
{
"type": "message",
"subtype": "channel_purpose",
"ts": "1358877455.000010",
"user": "U2147483828",
"purpose": "whatever",
"text": "<@U2147483828|cal> set the channel purpose: whatever"
}
A channel_purpose message is sent when the purpose for a channel is changed
using the channel.setPurpose method.
When an event occurs, we will send an HTTP POST request to your Request URL. The outer payload is uniform across all Events API methods, and contains fields like team_id and event. Learn more