Add status to board list GraphQL API

What does this MR do and why?

As part of the configurable work item statuses initiative, this MR adds status to board list GraphQL API.

The status field will be used by the frontend in ee/app/assets/javascripts/boards/graphql/board_lists.query.graphql.

⚠️ This MR introduces a placeholder API to unblock the frontend for 18.1. Currently, the API returns nil for status data. We will start returning actual status data, likely at the beginning of 18.1, once creating board lists with status values is supported.

Notes

As per our decision log, we're implementing support for statuses in legacy issue boards, since work item lists won't be ready for GA by July 2025.

References

• BE: Add status to legacy issues GraphQL API
• Status lists on legacy issue boards
• Work Items Custom Status Design Doc
• Configurable Work Item Statuses Epic

Screenshots or screen recordings

backend only

How to set up and validate locally

1. Enable the work_item_status_feature_flag feature flag.
2. Create a new issue board under flightjs/Flight project.
3. Use the queries below to verify the results.

View query

query BoardList($fullPath: ID!, $boardId: BoardID!) {
  project(fullPath: $fullPath) {
    id
    board(id: $boardId) {
      id
      lists {
        nodes {
          id
          title
          milestone {
            title
          }
          status {
            id
            name
            color
            color
          }
        }
      }
    }
  }
}

{
  "fullPath": "flightjs/Flight",
  "boardId": "gid://gitlab/Board/6" # TODO: Replace with your board GID
}

View response

{
  "data": {
    "project": {
      "id": "gid://gitlab/Project/7",
      "board": {
        "id": "gid://gitlab/Board/6",
        "lists": {
          "nodes": [
            {
              "id": "gid://gitlab/List/11",
              "title": "Open",
              "milestone": null,
              "status": null
            },
            {
              "id": "gid://gitlab/List/12",
              "title": "Closed",
              "milestone": null,
              "status": null
            }
          ]
        }
      }
    }
  },
  "correlationId": "01JSX4VNJ6ZQR3XEE7JFA6GRV4"
}

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