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pinned_item message event

An item was pinned in a channel

Compatibility: RTM

    "type": "message",
    "subtype": "pinned_item",
    "user": "U024BE7LH",
    "item_type": "F",
    "text": "<@U024BE7LH|cal> pinned their Image <https:...7.png|7.png> to this channel.",
    "item": {
    "channel": "C02ELGNBH",
    "ts": "1360782804.083113"

The pinned_item message is sent when an item is pinned to a channel.