Optional extraOptional faceTavus face id. Falls back to TAVUS_FACE_ID.
Optional palTavus pal id. Falls back to TAVUS_PAL_ID; defaults to a stock pal when omitted.
Optional personaUse palId instead.
Optional propertiesConversation properties passed through to Tavus.
Optional replicaUse faceId instead.
Additional fields to merge into the Tavus conversation creation payload.