Session API for Temporary Number Masking

The Session API is the core number-masking primitive: send two real numbers and get back a virtual number that connects them in both directions. Routing is decided by who is calling, so the same number works whether Party A or Party B dials it. Sessions are idempotent on your own reference id (an order, ride or ticket id), so retries safely return the existing session instead of allocating a new number. Set an expiry so the number stops routing automatically once the order is done, cap the number of calls, or pause and resume routing at any time — all over a single REST endpoint.