A message was sent to a channel
{
"type": "message",
"subtype": "channel_join",
"ts": "1358877458.000011",
"user": "U2147483828",
"text": "<@U2147483828|cal> has joined the channel",
"inviter": "U123456789"
}
The channel_join event is sometimes sent to all connections for a user when that user leaves a channel. It is sometimes withheld.
If the user was invited, the message will include an inviter property
containing the user ID of the inviting user. The property will otherwise be absent.
If you prefer a more atomic event, use member_joined_channel instead. Consult the changelog for further guidance.
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