Initial implementation by GitLab Duo.

Since it is a required field.

- Disclose the mutation causing an `GraphQLResponseError`
- Use `ErrorResponse` to return inline errors
- Create the generic `ErrEmptyResponse` error and return it if creation of a
  work item succeeds, but no work item is returned

Also add comprehensive unit testing.

Co-Authored-By: Timo Furrer <tfurrer@gitlab.com>

feat(workitems): Implement `CreateWorkItem()`.

See merge request !2751

## 2.2.0

### 🚀 Features

- feat(workitems): Implement `CreateWorkItem()`. ([!2751](!2751)) by [Florian Forster](https://gitlab.com/fforster)

# [2.2.0](https://gitlab.com/gitlab-org/api/client-go/compare/v2.1.0...v2.2.0) (2026-03-04)

### Bug Fixes

* **workitems:** move nil guard to top of wrap() and regenerate mock ([01f38fca](01f38fca))

### Features

* **workitems:** add CreateTestWorkItem helpers to utils_test.go ([10ff8a35](10ff8a35))
* **workitems:** Implement `CreateWorkItem()`. ([07ee38c5](07ee38c5))