post
https://api.banking.netevia.dev/api/lockbox//rules
Creates one new split funding rule on the given lockbox account and returns the created rule.
The account must exist and be a lockbox (IsLockAccount = true). Validation runs before anything is written: transfer-type-conditional fields, percentage range, the 100% cap across active rules, and the duplicate check. A create that would push the active total over 100% is rejected outright — the rule is not stored in an inactive state as a consolation.