curl -L -X GET "https://api.box.com/2.0/integration_mappings/slack?partner_item_id=C987654321&box_item_id=123456789" \
     -H "authorization: Bearer <ACCESS_TOKEN>"

{
  "limit": 1000,
  "next_marker": "JV9IRGZmieiBasejOG9yDCRNgd2ymoZIbjsxbJMjIs3kioVii",
  "entries": [
    {
      "id": "12345",
      "type": "integration_mapping",
      "partner_item": {
        "id": "C12378991223",
        "type": "channel",
        "slack_org_id": "E1234567"
      },
      "box_item": {
        "id": "12345",
        "type": "folder",
        "etag": "1",
        "sequence_id": "3",
        "name": "Contracts"
      },
      "integration_type": "slack",
      "is_manually_created": true,
      "options": {
        "is_access_management_disabled": true
      },
      "created_by": {
        "id": "11446498",
        "type": "user",
        "name": "Aaron Levie",
        "login": "ceo@example.com"
      },
      "modified_by": {
        "id": "11446498",
        "type": "user",
        "name": "Aaron Levie",
        "login": "ceo@example.com"
      },
      "created_at": "2012-12-12T10:53:43-08:00",
      "modified_at": "2012-12-12T10:53:43-08:00"
    }
  ]
}