GraphQL: Expose `assignees`, `labels` and `milestone` on issue boards
For gitlab#218040 we'll need some additional associations to be exposed under `board`. At the moment, here are our options ![image](/uploads/3867cd1b11320e0305a701049f9ea8bc/image.png) Add board associations: - `milestone` (via board.milestone_id) - `assignees` (via `board_assignees`) - `labels` (via `board_labels`) ![image](/uploads/fa18c9f0169d38ed0bdeb2e7af2b0ae3/image.png)
epic