What problem does it solve? Domain guard checks that require async I/O — such as verifying a referenced entity exists via an adapter or repository — cannot live in synchronous validators or directly in domain aggregates. This Skill scaffolds a named, independently testable CoreEx policy class in Application/Policies/ that encapsulates those guards and composes cleanly into Result<T> pipelines. ## Core Features & Use Cases - EnsureExists Guards: Fetch an entity through an adapter and translate NotFoundError into a field-level ValidationError (HTTP 400) or a NotFoundException with WithErrorCode/WithKey (HTTP 404), depending on whether the id is a body property or path parameter. - Business Rule Guards: Implement state/condition checks (e.g. EnsureActiveAsync) returning Result.BusinessError with machine-readable error codes. - Localizable Messages: Use LText static fields for entity names inside error messages while keeping property names as plain strings via MessageItem.CreateErrorMessage. - Unit Test Generation: Produce matching {Name}PolicyTests.cs with Moq-based adapter mocks covering success, validation-error, and business-error paths. - Use Case: When building an order service that must verify a product exists and is active before adding it to a basket, generate a ProductPolicy with EnsureExistsAsync and EnsureActiveAsync, then compose it into the service's Result.GoAsync().ThenAsAsync() pipeline. ## Quick Start Ask the AI to create a CoreEx policy class that ensures a referenced entity exists via its adapter, returning the loaded entity as Result<T> with a matching unit test class.
