feature: cucumber integration

[jirikuncar]

Adds integration for 🥒 Cucumber.

[ericmustin]

This approach generally seems ok but per my comments let's move using the include / prepend pattern here instead of class_eval.

@marcotc Can you take a look at the usage of Pin here? Is there a more appropriate pattern to use in this case?

[marcotc]

I think the changes are looking good!

One thing I noticed is that some of the patterns used (like the Pin, or the Integration#patch implementation) are following patterns that we no longer want to follow.

Here's an example of a very recent integration: https://github.com/DataDog/dd-trace-rb/pull/1121/files

And the relevant part when it comes to creating the actual tracing span:

dd-trace-rb/lib/ddtrace/contrib/sneakers/tracer.rb

Lines 15 to 44 in 52926d7

	def call(deserialized_msg, delivery_info, metadata, handler)
	trace_options = {
	service: configuration[:service_name],
	span_type: Datadog::Ext::AppTypes::WORKER
	}
	request_span = tracer.trace(Ext::SPAN_JOB, trace_options)
	# Set analytics sample rate
	if Datadog::Contrib::Analytics.enabled?(configuration[:analytics_enabled])
	Datadog::Contrib::Analytics.set_sample_rate(request_span, configuration[:analytics_sample_rate])
	end
	# Measure service stats
	Contrib::Analytics.set_measured(request_span)
	request_span.resource = @app.to_proc.binding.eval('self.class').to_s
	request_span.set_tag(Ext::TAG_JOB_ROUTING_KEY, delivery_info.routing_key)
	request_span.set_tag(Ext::TAG_JOB_QUEUE, delivery_info.consumer.queue.name)
	if configuration[:tag_body]
	request_span.set_tag(Ext::TAG_JOB_BODY, deserialized_msg)
	end
	@app.call(deserialized_msg, delivery_info, metadata, handler)
	rescue StandardError => e
	request_span.set_error(e) unless request_span.nil?
	raise e
	ensure
	request_span.finish if request_span
	end

Overall, removing the Pin and simplifying the Integration class is what I see as left to bring this PR up to our latest patterns.

[marcotc]

Can tests be nested in Cucumber? I'm wondering if it's possible that @current_feature_span is assigned a value more than once before being consumed in #on_test_case_finished.

[jirikuncar]

@ericmustin thank you for the review.

Min version (were events not part of the api before 4.0?)

✅ there are some minor differences - in version 3 the events were sent for step hooks too.

Nested Steps

🗑️ not supported - not implemented

We need to add documentation

✅ done

[ericmustin]

@jirikuncar sounds good, will try to have a final pass here before eod...i'll look into whatever those build issues are, seems unrelated to this PR

[ericmustin]

🚀 I left the most minor of nits, otherwise LGTM. nice work @jirikuncar !

[jirikuncar]

@ericmustin good catch! Thanks