Delete interest tier schedule

Delete an interest tier schedule entry.

Returns:

• 400 Bad Request: Invalid effective_date format OR attempting to delete the earliest tier schedule entry for a non-PENDING account
• 404 Not Found: Tier schedule entry not found for the given effective_date OR ledger account not found

Note: PENDING accounts can delete the earliest tier schedule entry (account hasn't opened yet). Active/non-PENDING accounts cannot delete the earliest entry to prevent orphaning the account.

If the deleted tier schedule has a past effective_date and the account is ACTIVE, the loan tape rebuild configuration will be updated to trigger rebuilds from that date.