feat: add reCAPTCHAv2 to registration form

[BradenM]

Changes

• Adds recaptcha gem dependency.
• Adds reCAPTCHAv2 checkbox to registration form.

Breaking

• Env Requirement: RECAPTCHA_SITE_KEY
• Env Requirement: RECAPTCHA_SECRET_KEY

Note

Originally spent a while trying to implement reCAPTCHAv3 (doesn't require the checkbox form, validates user based on input/actions on site) but wasn't able to get it to work. Believe it may be related to ambethia/recaptcha#342 considering we are also using TurboLinks.

@aarontitus, also means the keys you grabbed previously aren't going to work. Need to regenerate a new site/secret key pair for v2.

[arroyoDev]

Once we have the new keys and all this looks good, I will reach out to @tsanders and ask him to push this and the other commit with IP address tracking to Staging and Live when he can.