Instrument filters in the pipeline

[mtodd]

This makes HTML::Pipeline compatible with ActiveSupport::Notifications instrumentation.

Shuffles things around a bit but adds instrumenting to every filter call.

@jch I know we talked about putting the instrumentation on the individual filters but I decided to keep it here since I wanted to make it easy to make the instrumentation service object available. The pipeline felt like the right place to put that, and the individual filter wasn't aware of the pipeline object as far as I could see.

[jch]

How about adding an instrumentation_service class attribute in addition to the instance attribute? If you have several pipelines defined, it'd be nice to default the instance attribute from the class one.

HTML::Pipeline.default_instrumentation_service = SomeService.new

[mtodd]

@jch 👓

[jch]

Hawt. Add a blurb about this in the readme?

[mtodd]

@jch now that I write the README, does it make sense to instrument the whole pipeline call, too? That would fire off a call_pipeline.html_pipeline event after all of the filters have finished.

[mtodd]

Rendered Markdown preview

[jch]

👍 adding an instrument to the pipeline call. I like that it gives you a quick total for all the filters. Thanks for the extra readme cleanup too.

[brianmario]

niiice

[mtodd]

@jch boom. Whatcha think?

[jch]

🤘 perfect sir. I'll cut a release after ci passes