List Available Attributes

List the attributes available for a category and region, with their display names and accepted values. Use this to discover what POST /v2/gbp/update-attributes/ will accept.

category must carry the gcid: prefix, for example gcid:plumber. A value without it is rejected.

When more results exist the response carries a next_token. Pass it back as next_token to fetch the next page. When it is absent you have reached the end.