Retrieve a specific Auditable entity

Creates a new child client under the authenticated client (or under a visible descendant via `parent_id`). The child is created for travel-data ingestion only: it inherits address, tax, currency, and methodology defaults from its parent, but has no credentials, no billing or purchasing capability, and no product or project access. Submit travel data for the new client by passing its `id` as the `client_id` on `POST /v2/travel-data`. The child is usable on the very next request after creation. Send `methodology_configuration` to configure the child's methodologies in the same request instead of inheriting the parent's. Omit it and the child gets a copy of the parent's current options — a copy, not a link: later changes on the parent never propagate to the child. Options that cannot be read as a list at all are rejected with `invalid_methodology_options` (`400`); options that are readable but not allowed — an unknown `activity_type` or `methodology`, two defaults for one activity type, more than three per type — are rejected with `invalid_methodology_options` (`422`). In both cases no client is created. Requires this feature to be enabled for your account (contact us); otherwise this endpoint responds with `404`.