New "enabled_assets" field on the account update request

Broker API

The account update request body now accepts an optional enabled_assets array, so enabled asset classes can be modified when updating an account.

• Omitting enabled_assets leaves the account's enabled assets unchanged.
• Updates are additive only: the submitted list must include every already-enabled asset, and assets cannot be removed.
• Enabling crypto for an equities-only account requires ["us_equity", "crypto"] plus the signed crypto agreement.
• The field uses the same asset class enum as the account creation request and the account response.

Affected Endpoints

• PATCH /v1/accounts/{account_id}