{
  "event": "room_message",
  "webhook_id": "23456",
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  "item": {
    "message": {
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      "from": {
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        "mention_name": "kinlane",
        "name": "Kin Lane"
      },
      "message": "@all migration to Slack scheduled for tomorrow.",
      "type": "message",
      "message_format": "text",
      "mentions": [
        {"id": 0, "mention_name": "all", "name": "All Members"}
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    },
    "room": {
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      "name": "API Evangelist",
      "links": {"self": "https://api.hipchat.com/v2/room/1234567"}
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}