Creates or replaces the active voice biometrics enrollment for a contact, associating it with a chosen enrollment phrase.
Use this endpoint to register a contact for active (phrase-based) voice biometrics authentication, after the contact has selected a phrase from the available catalog.

Only the enrollment intent is registered here — the actual voice sample is captured separately during a call via the call-level enrollment flow.
If the contact does not yet exist, it is created automatically and its consent is marked as granted.
The phrase_id must reference an existing phrase, otherwise the request returns 404. Re-issuing this request replaces the phrase association but preserves the existing consent state.