Add a way to skip a handler in the pipeline

[kzu]

When building the pipeline, sometimes it's useful for Use(...) to conditionally turn themselves off depending on some service or configuration. Rather than inject a passthrough DelegatingHandler needlessly, this allows these cases to return a WhatsAppHandler.Skip instead, which will not be added to the pipeline at all

[Copilot]

Pull Request Overview

This PR adds support for conditionally skipping handlers in the WhatsApp pipeline by returning a dedicated Skip handler.

• Refactors the handler invocations in the pipeline builder to check for Skip.
• Introduces a Skip handler type in WhatsAppHandler and updates the pipeline test accordingly.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/WhatsApp/WhatsAppHandlerBuilder.cs	Updates the pipeline builder to conditionally apply factories.
src/WhatsApp/WhatsAppHandler.cs	Adds a new Skip handler and updates related documentation.
src/Tests/PipelineTests.cs	Modifies tests to include the new Skip handler logic.

Comments suppressed due to low confidence (1)

src/WhatsApp/WhatsAppHandler.cs:20

• [nitpick] The class name 'SKipWhatsAppHandler' contains a typo with inconsistent capitalization. Consider renaming it to 'SkipWhatsAppHandler' for clarity and consistency.

    public static IWhatsAppHandler Skip { get; } = new SKipWhatsAppHandler();

[Copilot]

The factory method is invoked twice for the same index. Instead, consider assigning 'handler = current' when the current handler is not Skip to avoid potential side effects from the second invocation.

Suggested change

	handler = factories[i](handler!, services);
	handler = current;

[kzu]

🧪 Details on Ubuntu 24.04.2 LTS

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