[CAUTH-423] Add captcha in the sign-up flow

[jfromaniello]

Changes

Add support for captcha (svg-captcha and recaptcha) to the sign-up flow.

• required for customers who enabled captcha in the dashboard (currently hidden/preview mode).
• optional for customers who are testing captcha thru our feature flags. The previous version will fallback to the login view and require the captcha there.

References

https://auth0team.atlassian.net/browse/CAUTH-423

Testing

• This change adds unit test coverage
• This change adds integration test coverage
• This change has been tested on the latest version of the platform/language

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors
• All code quality tools/guidelines have been run/followed
• All relevant assets have been compiled
• All active GitHub checks have passed

[karlhorky]

hidden/preview mode

Does this indicate that CAPTCHAs are no longer Early Access as kusold mentioned in #1845 (comment) ?

If I could turn on the hidden mode, I would like to try this out, if possible.

Can't find any other public information about it...