Add 7 edge case tests for ApiClientBase:
- GetAsync_Returns200_EmptyBody_MapsToApiError
- GetAsync_Returns200_InvalidJson_MapsToApiError
- GetAsync_Returns204_ForUnitType_MapsToSuccess
- GetAsync_Returns204_ForNonUnitType_MapsToApiError
- GetAsync_NetworkException_MapsToApiError
- GetAsync_Timeout_MapsToApiError
- GetAsync_Returns400_WithoutValidationFormat_MapsToApiError
Also fix bug in ApiClientBase where 204 NoContent for Unit type
failed due to incorrect type casting. The implicit conversion from
Unit to ApiResult<Unit> must be applied before the runtime cast.
- Add GetAsync_Returns404_MapsToNotFound test
- Add GetAsync_Returns400_WithValidationErrors_MapsToValidationError test
- Add GetAsync_Returns401_MapsToUnauthorized test
- Add GetAsync_Returns403_MapsToForbidden test
- Add GetAsync_Returns500_MapsToApiError test
- Add FrameworkReference to Microsoft.AspNetCore.App for ValidationProblemDetails