New fields for `boards` queries

We've added two new fields for boards queries:

1. access_level: Returns an enum value that specifies the user's board permission level.
2. object_type_unique_identifier: Returns a unique identifier for the board's object type.

query {
  boards (ids: 1234567890) {
    access_level
    object_type_unique_identifier
    items_page {
      items {
        id
        name
      }
    }
  }
}