GRPC for Google write operations + compression

[tdutreui-solocal]

• Prevent write operation duplicates (see Equivalent of VCR testing using this gem googleads/google-ads-ruby#244)
• Adds Zlib compression
• Better error message for missing recordings
• Added the GCR_RECORD envvar so that you can override an existing cassette

[danielmbarlow]

Suggested change

	def compress
	def compress?

[tdutreui-solocal]

Applied, thx

[danielmbarlow]

Thanks TD. Just had a smal comment to make about a minor detail

[danielmbarlow]

This is a little difficult to read maybe we could extract some variables and improve the whitespace

[tdutreui-solocal]

@asux Hi !
Do you accept Pull requests?

I propose you these improvements that we have been testing for some months now, without major issues.
We are using Rspec + VCR + GCR to make integration tests with the Google Ads API (using the official client)
The only downside is that sometimes Rspec hangs at the end of the execution, so we had to add this at_exit hook to circumvent it, in a shared context.

RSpec.shared_context "using GCR and VCR" do
  around(:example) do |ex|
    cassette_name = ex.metadata[:full_description].parameterize.underscore
    VCR.use_cassette(cassette_name) do
      GCR.with_cassette cassette_name do
        ex.run
      end
    end
  end

  at_exit do
    GCR.stub.instance_variable_get(:@ch).close
    GC.start # garbage collects stuff might fix Rspec hangs, see https://github.com/grpc/grpc/issues/38442
  end
end

[asux]

Hi @tdutreui-solocal. I'm bit loose context about this GCR, since not use it in recent project. Generally, your code makes sense to me.