feat: Move OTEL hooks to the SDK

[askpt]

Move OTEL hooks to the SDK

This pull request introduces telemetry enhancements to the OpenFeature .NET SDK by adding new hooks for tracing and metrics, updating dependencies, and providing examples and tests. The most significant changes include the addition of the TraceEnricherHook and MetricsHook classes, integration of OpenTelemetry in the ASP.NET Core sample, and updates to dependencies to support telemetry features.

Telemetry Enhancements

• Trace Enricher Hook: Added TraceEnricherHook to enrich telemetry traces with feature flag evaluation details, including tags and events for tracing purposes. This hook integrates with the current Activity and supports error handling.
• Metrics Hook: Introduced MetricsHook for capturing metrics such as evaluation requests, successes, errors, and active evaluations. Metrics are collected using OpenTelemetry's Meter API. [1] [2]

Dependency Updates

• OpenTelemetry Dependencies: Added OpenTelemetry.Extensions.Hosting, OpenTelemetry.Instrumentation.AspNetCore, and OpenTelemetry.Exporter.OpenTelemetryProtocol to the ASP.NET Core sample project to support telemetry features. [1] [2]
• DiagnosticSource Dependency: Included System.Diagnostics.DiagnosticSource in the main project and centralized dependency management. [1] [2]

Documentation and Examples

• README Updates: Added documentation for TraceEnricherHook and MetricsHook, including detailed descriptions, examples, and usage instructions for integrating these hooks with OpenTelemetry.
• ASP.NET Core Sample: Updated the sample application to demonstrate the use of TraceEnricherHook and MetricsHook with OpenTelemetry tracing and metrics. [1] [2]

Testing

• MetricsHook Tests: Added unit tests for MetricsHook to verify metrics collection during different stages of feature flag evaluation (e.g., BeforeAsync, AfterAsync, ErrorAsync, FinallyAsync).

Related Issues

Fixes #175

Notes

• In this PR I made some changes to the samples application. This allow us to see the metrics and traces in any OTEL tool.

Check the screenshots below:

Follow-up Tasks

• We should remove any reference in the other repository and mark the Nuget package as deprecated.

[codecov]

Codecov Report

Attention: Patch coverage is 95.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.23%. Comparing base (39f884d) to head (2b4306a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/OpenFeature/Hooks/MetricsHook.cs	94.00%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #338      +/-   ##
==========================================
+ Coverage   87.02%   87.23%   +0.21%     
==========================================
  Files          45       47       +2     
  Lines        1757     1794      +37     
  Branches      184      182       -2     
==========================================
+ Hits         1529     1565      +36     
- Misses        188      190       +2     
+ Partials       40       39       -1     

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[beeme1mr]

Thanks for starting this PR but I think we should wait until this spec PR is merged before moving this hook to the SDK.

[askpt]

@beeme1mr, @toddbaert, @kinyoklion, and @kylejuliandev, I made a couple of changes since your last review. Please look to see if they make sense.