Adjust lifecycleUpdate mutation to prevent removal of mapped statuses

What does this MR do and why?

Currently, the lifecycleUpdate mutation (introduced in !192988 (merged)) prevents deletion of a custom status in the following cases:

1. The status is in use (i.e., explicitly assigned to a work item).
2. The status is set as one of the lifecycle's default statuses (e.g., open, closed, duplicated).

This MR adds support for a third condition:

3. A status cannot be deleted if it was created during the transition from system-defined to custom statuses and has a recorded mapping. These mapped statuses (e.g., To do, Done, Duplicate) can still be updated but not removed.

Additionally, this MR fixes a minor bug where the status mapping (converted_from_system_defined_status_identifier) was not being recorded when creating a custom status during the switch from system-defined to statuses.

References

• BE: Implement lifecycle and status management APIs
• BE: Add mutation to update lifecycle
• Work Items Custom Status Design Doc
• Configurable Work Item Statuses Epic

Screenshots or screen recordings

When trying to delete a status when transitioning from a system-defined to a custom lifecycle

When trying to delete a status in use - that either is explicitly assigned to a work item or has an existing mapping

When trying to delete a status that is set as one of the lifecycle's default statuses

When a status is deleted successfully

How to set up and validate locally

1. Enable the work_item_status_feature_flag feature flag.
2. Run a mutation to create a custom lifecycle and statuses from the system-defined ones.

View mutation

mutation UpdateLifecycle($input: LifecycleUpdateInput!) {
  lifecycleUpdate(input: $input) {
    lifecycle {
      id
      name
      statuses {
        id
        name
      }
      defaultOpenStatus {
        id
        name
      }
      defaultClosedStatus {
        id
        name
      }
      defaultDuplicateStatus {
        id
        name
      }
    }
    errors
  }
}

{
  "input": {
    "namespacePath": "gitlab-org",
    "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Lifecycle/1",
    "statuses": [
      {
        "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Status/1",
        "name": "To do",
        "color": "#737278",
        "description": null,
        "category": "TO_DO"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Status/2",
        "name": "In progress",
        "color": "#1f75cb",
        "description": null,
        "category": "IN_PROGRESS"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Status/3",
        "name": "Done",
        "color": "#108548",
        "description": null,
        "category": "DONE"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Status/4",
        "name": "Won't do",
        "color": "#DD2B0E",
        "description": null,
        "category": "CANCELLED"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::SystemDefined::Status/5",
        "name": "Duplicate",
        "color": "#DD2B0E",
        "description": null,
        "category": "CANCELLED"
      }
    ],
      "defaultOpenStatusIndex": 0,
      "defaultClosedStatusIndex": 2,
      "defaultDuplicateStatusIndex": 4
  }
}

1. Run a mutation to attempt to delete a status in use - that either is explicitly assigned to a work item or has an existing mapping.

View mutation

mutation UpdateLifecycle($input: LifecycleUpdateInput!) {
  lifecycleUpdate(input: $input) {
    lifecycle {
      id
      name
      statuses {
        id
        name
      }
      defaultOpenStatus {
        id
        name
      }
      defaultClosedStatus {
        id
        name
      }
      defaultDuplicateStatus {
        id
        name
      }
    }
    errors
  }
}

{
  "input": {
    "namespacePath": "gitlab-org",
    "id": "gid://gitlab/WorkItems::Statuses::Custom::Lifecycle/35",
    "statuses": [
      {
        "id": "gid://gitlab/WorkItems::Statuses::Custom::Status/157",
        "name": "To do",
        "color": "#737278",
        "description": null,
        "category": "TO_DO"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::Custom::Status/158",
        "name": "In progress",
        "color": "#1f75cb",
        "description": null,
        "category": "IN_PROGRESS"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::Custom::Status/159",
        "name": "Done",
        "color": "#108548",
        "description": null,
        "category": "DONE"
      },
      {
        "id": "gid://gitlab/WorkItems::Statuses::Custom::Status/161",
        "name": "Duplicate",
        "color": "#DD2B0E",
        "description": null,
        "category": "CANCELLED"
      }
    ],
      "defaultOpenStatusIndex": 0,
      "defaultClosedStatusIndex": 2,
      "defaultDuplicateStatusIndex": 3
  }
}

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