Add support for reCAPTCHA Enterprise

Reroll against latest dev.

At this point we should be using "v1" instead of the "v1beta1" per the documentation (https://cloud.google.com/recaptcha-enterprise/docs/migration-v1).

If you are using v1beta1 to create and annotate assessments, we recommend using v1because the new features, such as reCAPTCHA Enterprise account defender are available only on v1. v1 supports both API key and service account authentication.

Also the url that's constructed is pointing to the site secret and for enterprise it should be pointing to the site key instead.

Started an MR with the patch applied and the URL targeting v1 - required updating how the score is accessed in the API response.

Also the url that's constructed is pointing to the site secret and for enterprise it should be pointing to the site key instead.

@oheller - can you clarify this?

Not really sure what's going on with the last commits to the merge request, but it doesn't apply to 1.x-dev or 1.0.0-beta9. I have attached a version that does apply.

Since Google is transitioning to the Enterprise model before the end of the year, this looks super important to get in?

Is the patch something that I can use on a production website? Or is more testing needed?
Is this backwards compatible with captcha keys that have not been migrated yet?

@weseze we've been using it on production for a long time. I'm not sure what you mean regarding BC though.

If we would include this patch on our Drupal setup, would sites that have "old" / "unmigrated" keys still work?
All of our websites that have recaptcha shoul be on a Google Cloud project and can use the enterprise variant of the script.
But I want to sure that if there are still websites with captcha keys that have not been migrated (yet), they will also work on the enterprise script.
Or is that simply not an issue?