Set the on-chain allowances the venue needs

Grants the venue's contracts the token approvals they need, signed custodially with your delegated key. Idempotent in effect: an already-sufficient allowance is not re-sent, and the corresponding *_tx_hash comes back null. The three identity fields in the body are required by the schema but are validated against the authenticated caller — they can confirm authority, never grant it. A mismatch, or a wallet you do not own, is a 403. Self-custody callers on the external-signing lane should use POST /v2/onchain/intent with op: "approvals" instead, and sign the approvals themselves. Auth & scope. Requires trade:execute, the mutation gate (API-key triple satisfies it), and a current Turnkey policy version.