Adds cancellationtoken to the FeatureEvaluationContext- and respects …

[rossgrambo]

This pull request introduces a cancellation mechanism to the feature evaluation process in the Microsoft.FeatureManagement library. The changes ensure that long-running feature evaluations can be cancelled if needed, improving the responsiveness and control over feature management operations.

Key changes include:

Cancellation Token Integration:

• src/Microsoft.FeatureManagement/FeatureFilterEvaluationContext.cs: Added a CancellationToken property to the FeatureFilterEvaluationContext class to support cancellation of feature evaluation operations.

Cancellation Checks:

• src/Microsoft.FeatureManagement/FeatureManager.cs: Added checks for cancellationToken.IsCancellationRequested in the IsEnabledAsync method to allow for early termination of the evaluation loop if cancellation is requested.
• src/Microsoft.FeatureManagement/FeatureManager.cs: Updated the FeatureFilterEvaluationContext instantiation to include the CancellationToken in the IsEnabledAsync method.
• src/Microsoft.FeatureManagement/FeatureManager.cs: Added checks for cancellationToken.IsCancellationRequested in the AssignVariantAsync method to handle cancellation during user, group, and percentile allocations. [1] [2] [3]

These updates enhance the robustness of the feature management system by allowing operations to be cancelled gracefully, which can be particularly useful in scenarios where feature evaluations are time-sensitive or resource-intensive.

Addresses #531

[Copilot]

Pull Request Overview

This PR introduces a cancellation mechanism to the feature evaluation process in the Microsoft.FeatureManagement library, allowing for early termination during long-running feature evaluations.

• Added a CancellationToken property to FeatureFilterEvaluationContext.
• Integrated cancellation checks into the IsEnabledAsync and AssignVariantAsync methods to handle cancellation requests efficiently.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Microsoft.FeatureManagement/FeatureManager.cs	Added cancellation checks in evaluation loops for feature enabled and variant assignment methods.
src/Microsoft.FeatureManagement/FeatureFilterEvaluationContext.cs	Added a CancellationToken property to support cancellation in feature filters.