action>: SendSlackMessage
buttons: [{"type":"button","text":{"type":"plain_text","text":"承認"},"value":"{\"workflow_id\":3,\"response_params\":{\"val\":\"あなた\",\"response_message\":\"確認しました\"}}","style":"primary"},{"type":"button","text":{"type":"plain_text","text":"否認"},"value":"{\"workflow_id\":null,\"response_params\":\"\"}","style":"danger"}]
# "timestamp": 1627852017,
# "mimetype": "application/pdf",
# "public_url_shared": false,
# "display_as_bot": false,
# "url_private": "https://files.slack.com/files-pri/hoge.pdf",
# "url_private_download": "https://files.slack.com/files-pri/hoge.pdf",
# "media_display_type": "unknown",
# "thumb_pdf": "https://files.slack.com/files-tmb/hoge.png",
# "permalink": "https://tutorial-123456.slack.com/files/hoge.pdf",
# "permalink_public": "https://slack-files.com/hoge",
# "reply_users_count": 0,
# "ts": "1627852018.001200",
# "channel_name": "test",
# "share_user_id": "123456"
# "has_rich_preview": false
# "ts": "1627852018.001500",
# "ts": "1627852018.001500",
# "name": "Robotic Crowd",
# "image_36": "https://avatars.slack-edge.com/hoge.png",
# "image_48": "https://avatars.slack-edge.com/hoge.png",
# "image_72": "https://avatars.slack-edge.com/hoge.png"
# "text": "ボタンと返信メッセージ付き",
# "dispatch_action": false,
# "type": "plain_text_input",
# "action_id": "plain_text_input-action",
# "dispatch_action_config": {
# "trigger_actions_on": [
# "value": "\"{\\\"workflow_id\\\":3,\\\"response_params\\\":{\\\"val\\\":\\\"あなた\\\",\\\"response_message\\\":\\\"確認しました\\\"}}\""
# "value": "\"{\\\"workflow_id\\\":null,\\\"response_params\\\":\\\"\\\"}\""