Add EFCore to example

[martincostello]

Changes

Add EFCore endpoint to assert on OpenTelemetry.Instrumentation.EntityFrameworkCore in OATS.

SQLite is used as the SQL Server variant goes through the existing SQL instrumentation so it misses the point of testing that EFCore specifically is instrumented.

Merge requirement checklist

• Unit tests added/updated
• CHANGELOG.md file updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[Copilot]

Pull Request Overview

This PR adds an EFCore endpoint to the ASP.NET Core example to test OpenTelemetry instrumentation specific to EFCore using SQLite.

• Added Microsoft.EntityFrameworkCore.Sqlite package and updated Swashbuckle in the project file.
• Introduced new TodoApp endpoints, repository, and entity models to enable EFCore functionality.
• Updated docker-compose configuration to include the new endpoint and trace queries.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

File	Description
examples/net8.0/aspnetcore/aspnetcore.csproj	Added EFCore Sqlite package and upgraded Swashbuckle version.
examples/net8.0/aspnetcore/TodoAppEndpoints.cs	Introduced TodoApp endpoints, repository, and EFCore context for the Todo application.
examples/net8.0/aspnetcore/Program.cs	Registered the TodoApp endpoints in the application startup.
docker/docker-compose-aspnetcore/oats.yaml	Included the new /api/todo/items endpoint and trace validation for EFCore instrumentation.

Comments suppressed due to low confidence (1)

examples/net8.0/aspnetcore/TodoAppEndpoints.cs:103

• The CompleteItemAsync method returns a nullable bool to indicate a not found item, while DeleteItemAsync returns a non-nullable bool. Consider unifying the return types to provide a consistent API design for repository methods.

public async Task<bool?> CompleteItemAsync(Guid itemId)

[martincostello]

I should add some metric assertions too (e.g. db_client_operation_duration_seconds).

[martincostello]

db_client_operation_duration_seconds

db.client.operation.duration wasn't added until version 1.11.0-beta.1 of OpenTelemetry.Instrumentation.SqlClient.

We can add it after updating to the latest NuGet packages.