Act as a Senior .NET Developer. Based on the following JSON response from [System Name], generate a set of C# records for DTOs. Use PascalCase, include `JsonPropertyName` attributes, and ensure all collection types are `IReadOnlyList<T>`.
I have a service `OrderService.cs` that depends on `IRepository` and `INotificationService`. Generate a suite of NUnit tests using **Moq**. Include a setup method and test cases for: 1) Success path, 2) Null input handling, and 3) Exception handling when the repository fails.
- EF Core optimizations ```
Review this LINQ query for EF Core. Identify potential **N+1 query issues** and suggest where `Include()` or `ThenInclude()` is needed. Suggest a projection using `.Select()` to avoid pulling back unnecessary columns.
- 🗂 Type:: note
- 🏷️ Tags::
- 📡 Status:: #status/🌱