More complete support for custom passwordless connections

[peter-isgfunds]

Changes

In a previous PR #1981 a new parameter useCustomPasswordlessConnection was introduced for the Lock configuration. The reason for that change was that it is possible to create passwordless connections outside of the default sms and email. That PR mentions that it can be done via Management API, and it would seem that this includes Terraform (https://github.com/auth0/terraform-provider-auth0) where it seems to be the only way to use passwordless connections.

This PR "completes" the above-mentioned PR where the connection parameter in connection/passwordless/actions.js -> logIn was still hard-coded to either sms or email

References

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 code quality tools/guidelines have been run/followed
• All relevant assets have been compiled

[stevehobbsdev]

Thanks for the contribution!