New `timeline_item` fields

In 2025-01, we added the following fields to the timeline_item endpoint:

content: Returns the content of the timeline item
created_at: Returns the creation date of the timeline item

query {
  timeline_item (id: 1234567890) {
    board {
      id
    }
    item {
      name
    }
    id
    user {
      id
      name
    }
    title
    type
    content
    created_at
  }
}