Migrate solution to .slnx and add DI/startup test coverage for observability registrations

[Copilot]

Repository still used a legacy .sln and had no test coverage for the package's DI/startup registration paths (AddObservability*), despite all projects already targeting net9.0;net10.0 with SDK-style project files.

Solution format

• Converted src/MX.Observability.ApplicationInsights.sln to src/MX.Observability.ApplicationInsights.slnx via dotnet sln migrate; removed the legacy .sln.
• Updated AGENTS.md and .github/copilot-instructions.md references accordingly.
• Confirmed no legacy project format or workflow changes were needed: all projects are SDK-style, and the reusable dotnet-ci action already auto-discovers solutions and caches keyed on **/*.slnx.

Test coverage

Added unit tests for previously-untested DI wiring:

• Core: AddObservabilityCore, AddAuditLogging, AddJobTelemetry — registration, lifetimes, safe-default option binding.
• AspNetCore/WorkerService adapters: AddObservability registers core services and correctly wires TelemetryFilterProcessor into the Application Insights SDK's ITelemetryProcessorFactory pipeline:

services.AddObservability();
using var provider = services.BuildServiceProvider();

var factory = Assert.Single(provider.GetServices<ITelemetryProcessorFactory>());
Assert.IsType<TelemetryFilterProcessor>(factory.Create(new NullTelemetryProcessor()));

Dependency fix (test-only)

Referencing the AspNetCore/WorkerService adapter projects from the test project surfaced a diamond-dependency conflict: Microsoft.ApplicationInsights.AspNetCore 2.23.0 transitively pulls Microsoft.Extensions.DependencyInjection 2.1.1, which collides with the net9/net10 framework-provided version (CS0433 ambiguous ServiceCollection). Pinned an explicit Microsoft.Extensions.DependencyInjection 10.0.11 PackageReference in the test project only — no production package versions changed.

• Fixes Modernise .NET solution and target framework #24

[Copilot]

🟢 Approval recommended

The changes are scoped to solution modernisation and additive test coverage, with only minor follow-up nits identified in the new test code.

Pull request overview

Modernises the repository’s solution format to .slnx and adds targeted unit tests that exercise the public DI/startup registration surface (AddObservability*) across the core library and host adapters, aligning with the repo’s multi-targeted net9/net10 setup.

Changes:

• Migrated the solution from legacy .sln to SDK-style .slnx, removed the old .sln, and updated documentation references.
• Added DI/startup-focused unit tests for core registrations (AddObservabilityCore, AddAuditLogging, AddJobTelemetry) and adapter registrations (ASP.NET Core + WorkerService AddObservability).
• Updated the test project to reference adapter projects and pinned Microsoft.Extensions.DependencyInjection to avoid the known diamond-dependency ambiguity; added Microsoft.AspNetCore.App framework reference for adapter test compilation.

File summaries

File	Description
src/MX.Observability.ApplicationInsights.Tests/Extensions/ServiceCollectionExtensionsTests.cs	Adds unit tests covering core service registrations and option binding defaults/overrides.
src/MX.Observability.ApplicationInsights.Tests/AspNetCore/ServiceCollectionExtensionsTests.cs	Adds unit tests for ASP.NET Core adapter DI wiring and telemetry-processor integration.
src/MX.Observability.ApplicationInsights.Tests/WorkerService/ServiceCollectionExtensionsTests.cs	Adds unit tests for WorkerService adapter DI wiring and telemetry-processor integration.
src/MX.Observability.ApplicationInsights.Tests/MX.Observability.ApplicationInsights.Tests.csproj	Adds adapter project references, framework reference, and pins DI package to resolve transitive conflicts.
src/MX.Observability.ApplicationInsights.slnx	Introduces the new .slnx solution file.
src/MX.Observability.ApplicationInsights.sln	Removes the legacy .sln solution file.
AGENTS.md	Updates solution path and validation commands to use .slnx.
.github/copilot-instructions.md	Updates solution path and validation commands to use .slnx.

Review details

• Files reviewed: 8/8 changed files
• Comments generated: 2
• Review effort level: Lite

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details
nuget/Microsoft.Extensions.DependencyInjection	10.0.11	Unknown	Unknown

Scanned Files

• src/MX.Observability.ApplicationInsights.Tests/MX.Observability.ApplicationInsights.Tests.csproj

[sonarqubecloud]

Quality Gate passed

Issues
39 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud