curl --request POST \
  --url https://api-next.ofauth.com/v2/access/users/lists/:listId/users/:userId \
  --header 'apiKey: <api-key>' \
  --header 'x-connection-id: <api-key>'

{
  "list": {
    "id": "<string>",
    "type": "<string>",
    "name": "<string>",
    "sortList": [
      {
        "order": "<string>",
        "direction": "<string>"
      }
    ],
    "users": [
      {
        "id": 123,
        "username": "<string>",
        "name": "<string>",
        "isVerified": true,
        "avatar": "<string>",
        "avatarThumbs": {
          "c50": "<string>",
          "c144": "<string>"
        }
      }
    ],
    "usersCount": 123,
    "postsCount": 123,
    "order": "<string>",
    "direction": "<string>",
    "canUpdate": true,
    "canDelete": true,
    "canManageUsers": true,
    "canAddUsers": true,
    "canPinnedToFeed": true,
    "isPinnedToFeed": true,
    "canPinnedToChat": true,
    "isPinnedToChat": true
  },
  "userState": {
    "id": "<string>",
    "type": "<string>",
    "name": "<string>",
    "hasUser": true,
    "canAddUser": true,
    "cannotAddUserReason": "<string>"
  }
}