Partially updates deposit_configs.maturity_period, deposit_configs.overrides and deposit_configs.interest_capitalization_mode on an active deposit account attachment. The overrides fields are processed using three‑state PATCH semantics, allowing values to be added, changed, or cleared as part of the update.

• Omitted: Keeps the current value
• null: Removes the override; falls back through the cascade (program → product)
• Value: Replaces the current override with the supplied value

NOTES:

• At least one of deposit_configs.maturity_period, deposit_configs.overrides or deposit_configs.interest_capitalization_mode must be provided. A payload carrying only maturity_period is valid.
• The overrides envelope, if provided, must contain at least one field. Sending an empty object returns 400 EIBACC0315.
• renewal_term still requires ROLLOVER configured in maturity_instructions somewhere in the fallback sequence (400 EIBACC0310 otherwise).
• maturity_period changes the term in force and takes effect immediately, recalculating the current cycle's maturity date from the attachment's effective_date. It's accepted in both documented forms (unit+value or calendar_maturity_date) and doesn't follow the three-state semantics above: null is a no-op, not a removal.
• maturity_period and overrides.renewal_term are independent. renewal_term keeps applying at rollover only and never recalculates the current cycle's maturity date.
• When maturity_period changes, the schedules driven by the maturity date (maturity instruction, maturity notices) are re-evaluated against the new date.
• product_id and payout_account stay fixed after attach and are ignored if included in the request body. To change the payout account, use Update payout account for deposit account.

This endpoint generates an Account attachment updated event that includes the active term in data.maturity_period. If the account has an external account ID, the event also includes it in data.external_account_id.

The response returns external_account_id whenever the account has one; it is omitted for an account with no external identifier.