Convention pass per docs/coding-conventions.md (rules 5/8/10/11):
- Promote DurationUnit from a raw union type to a const tuple + derived type.
- Mongoose schema enum imports DurationUnits instead of inlining the values.
- Both validators import DurationUnits instead of inlining z.enum twice.
- Drop stale 'expiry' entries from openapi.json (spec is now strict-mode-correct).
- Collapse two refines into a single superRefine in createMaintenanceWindowBodyValidation; same on edit.
- Match peer migration convention: use mongoose.connection.db directly, not Model.collection.
- Tighten TTL index detection: require expireAfterSeconds + single-field key.
- Add Starting log at migration top to match peers 0003-0006.
Maintenance windows could disappear seconds after creation when the API received
a payload with end dates already in the past. The repository auto-set
expiry = end for one-time windows (repeat = 0), and Mongo's TTL index on the
expiry field then deleted the row on its next sweep. This was particularly
visible with automation tools sending payloads in non-UTC timezones.
## Changes
### Validator hardening
- Add .strict() to create + edit body schemas so unknown keys return 400
instead of being silently dropped.
- Refine end > start on create.
- Refine end > now for one-time create payloads (repeat = 0).
- Refine end > start on edit when both are provided.
- Remove the accepted expiry field from both schemas.
### Stop the auto-delete behaviour
- Repository.create no longer copies end into expiry.
- Schema's expiry field + TTL index removed.
- Migration 0007 drops the live TTL index and unsets stale expiry values on
existing rows so legacy data is no longer at risk.
### Client
- Form submission no longer includes expiry.
gorkem-bwl
Alex Holliday