Default APR tier guidance updated for cash interest enrollment

Broker API

The cash_interest schema description on Create Account now clarifies default APR tier behavior for High Yield Cash enrollment.

• An account created without cash_interest that signs the required Alpaca Customer Agreement revision may be enrolled in a default APR tier automatically.
• Partners should not rely on default-tier enrollment and should provide cash_interest with the desired apr_tier_name.
• status should still not be specified on enrollment; the response returns PENDING_CHANGE until the enrollment completes.

No fields, types, or behavior changed.

Affected Endpoints

• POST /v1/accounts