[Captcha] Implement the new captcha configuration

[louischan-oursky]

• [ ] Keep the old configuration intact
• [ ] Introduce the new configuration
  • The Go structs
  • The JSON schema
  • Write tests to test for valid and invalid configurations

[linear[bot]]

DEV-1411 [Captcha] Implement the new captcha configuration

[pkong-ds]

Keep the old configuration intact

old config use key captcha, which conflicts with new config key Maybe mark old one as captcha_legacy?

[louischan-oursky]

No. You add new fields to it directly. Just leave the legacy provider unchanged.