feat: AWS lambda programatic wrap

[joshwestbrook]

Our company uses container images for deploying our lambda functions and use herokuish Procfile entries as our entrypoints for the images.

This means it takes a ton of jiggery-pokery to get this working for our situation because:

1. We can't natively pull in a lambda layer without using the AWS S3 CLI to pull down the layer zip and copy into our base image
2. The _HANDLER environment variable actually contains our Procfile entry (which calls the lambda RIC under the hood with the handler that's expected by this wrapper)

This PR introduces an alternative way of instrumenting by programmatically wrapping an arbitrary handler method for scenarios where using lambda layers aren't an option (such as ours).

Example:

require 'opentelemetry/instrumentation/aws_lambda'

module Example
  class Handler
    extend OpenTelemetry::Instrumentation::AwsLambda::Wrap

    def self.process(event:, context:)
      pp event
    end
    instrument_handler :process
  end
end

[arielvalentin]

cc: @jterapin @alextwoods @NathanielRN

[kaylareopelle]

Thanks, @joshwestbrook! It's great to see the lambda instrumentation getting some use and I like your adjustment to make it more flexible for different scenarios.

Since @xuan-cao-swi initially wrote this, I'd like him to also take a look before we merge.

[joshwestbrook]

Thanks, @joshwestbrook! It's great to see the lambda instrumentation getting some use and I like your adjustment to make it more flexible for different scenarios.

Since @xuan-cao-swi initially wrote this, I'd like him to also take a look before we merge.

Awesome, thanks for taking a look at this @kaylareopelle!

[xuan-cao-swi]

Thanks @joshwestbrook , I think it looks good. Would you mind add some test case around the instrument_handler function.

[joshwestbrook]

Thanks @joshwestbrook , I think it looks good. Would you mind add some test case around the instrument_handler function.

Sure thing @xuan-cao-swi! I pushed up some tests for the instrument_handler method in c5994bc

I'm very used to using RSpec for specs so let me know if you have any recommendations for improvements 😄

[xuan-cao-swi]

Hi @joshwestbrook , just need linting from rubocop, then I can approve it.

[kaylareopelle]

@xuan-cao-swi - Rubocop linting has passed now! Can you take another look?