List recipients opted out of a message category

{
  "type": "object",
  "description": "OpenAPI shape for the paginated opt-outs response, so the generated clients get the\n{count, next, previous, results} envelope instead of an untyped object.",
  "required": [
    "count",
    "next",
    "previous",
    "results"
  ],
  "properties": {
    "count": {
      "type": "integer",
      "description": "Total number of opted-out recipients for the category."
    },
    "next": {
      "type": [
        "string",
        "null"
      ],
      "format": "uri",
      "description": "URL for the next page, or null on the last page."
    },
    "previous": {
      "type": [
        "string",
        "null"
      ],
      "format": "uri",
      "description": "URL for the previous page, or null on the first page."
    },
    "results": {
      "type": "array",
      "items": {
        "type": "object",
        "required": [
          "id",
          "identifier",
          "preferences",
          "updated_at"
        ],
        "properties": {
          "id": {
            "type": "string",
            "format": "uuid",
            "description": "Server-assigned UUID for this recipient's preference record."
          },
          "identifier": {
            "type": "string",
            "description": "The recipient identifier (e.g. email address)."
          },
          "preferences": {
            "description": "Map of category ID to preference status (`OPTED_IN`, `OPTED_OUT` or `NO_PREFERENCE`). The reserved `$all` key covers every marketing message.",
            "type": "object"
          },
          "updated_at": {
            "type": "string",
            "format": "date-time",
            "description": "When the preference was last updated."
          }
        }
      }
    }
  }
}