Support message_send_ttl_seconds for WhatsApp templates

We use POST /v1/whatsapp/templates to automatically provision Utility templates for each connected WABA.

Meta supports message_send_ttl_seconds, but Zernio’s current schema does not expose or pass this field through.

Our use case requires:

message_send_ttl_seconds: 600

so time-sensitive Utility messages expire after 10 minutes instead of using Meta’s 30-day API default.

Ideally, POST /v1/whatsapp/templates should accept and pass message_send_ttl_seconds through to Meta.

Support for updating the TTL as well, if Meta allows it, would also be useful.

Current impact: automatically provisioned templates cannot use a short TTL, which can allow stale Utility messages to be delivered long after they are relevant.