Validate phone for MFA setup

Validate the phone number for setting up MFA in the current organization. This validation requires the setupId and token from POST /v3/mfa/setup.

After the validation is complete, the phone number is registered for the MFA sign in operation.

There are two stages in the BILL MFA process.

1. MFA setup: Add a valid phone number for setting up MFA in the organization (with POST /v3/mfa/setup), and then complete the setup by validating the entered phone number (with POST /v3/mfa/validate). At this point, the phone number is registered for the MFA sign in operation.
2. MFA sign in: Generate an MFA challenge (with POST /v3/mfa/challenge), and then complete MFA sign in by validating the MFA challenge (with POST /v3/mfa/challenge/validate). At this point, your API session is MFA trusted.