refactor(maintenance): centralize DurationUnit + sync OpenAPI spec

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).

server/openapi.json

@@ -4657,11 +4657,6 @@
 									"repeat": {
 										"type": "number",
 										"minimum": 0
-									},
-									"expiry": {
-										"type": "string",
-										"nullable": true,
-										"format": "date-time"
 									}
 								},
 								"required": ["monitors", "name", "duration", "durationUnit", "start", "end", "repeat"]
@@ -5190,11 +5185,6 @@
 										"nullable": true,
 										"format": "date-time"
 									},
-									"expiry": {
-										"type": "string",
-										"nullable": true,
-										"format": "date-time"
-									},
 									"monitors": {
 										"type": "array",
 										"items": {

server/src/db/models/MaintenanceWindow.ts

@@ -1,5 +1,5 @@
 import { Schema, model, type Types } from "mongoose";
-import type { MaintenanceWindow } from "@/types/maintenanceWindow.js";
+import { DurationUnits, type MaintenanceWindow } from "@/types/maintenanceWindow.js";
 
 type MaintenanceWindowDocumentBase = Omit<MaintenanceWindow, "id" | "monitorId" | "teamId" | "start" | "end" | "createdAt" | "updatedAt"> & {
 	monitorId: Types.ObjectId;
@@ -38,7 +38,7 @@ const MaintenanceWindowSchema = new Schema<MaintenanceWindowDocument>(
 		},
 		durationUnit: {
 			type: String,
-			enum: ["seconds", "minutes", "hours", "days"],
+			enum: DurationUnits,
 		},
 		repeat: {
 			type: Number,

server/src/types/maintenanceWindow.ts

@@ -1,4 +1,5 @@
-export type DurationUnit = "seconds" | "minutes" | "hours" | "days";
+export const DurationUnits = ["seconds", "minutes", "hours", "days"] as const;
+export type DurationUnit = (typeof DurationUnits)[number];
 
 export interface MaintenanceWindow {
 	id: string;

server/src/validation/maintenanceWindowValidation.ts

@@ -1,5 +1,6 @@
 import { z } from "zod";
 import { booleanCoercion } from "./shared.js";
+import { DurationUnits } from "@/types/maintenanceWindow.js";
 
 const dateToString = z.coerce.date().transform((d) => d.toISOString());
 
@@ -13,7 +14,7 @@ export const createMaintenanceWindowBodyValidation = z
 		name: z.string().min(1, "Name is required"),
 		active: z.boolean().optional(),
 		duration: z.number().min(1, "Duration is required"),
-		durationUnit: z.enum(["seconds", "minutes", "hours", "days"]),
+		durationUnit: z.enum(DurationUnits),
 		start: dateToString,
 		end: dateToString,
 		repeat: z.number().min(0, "Repeat must be a non-negative number"),
@@ -71,7 +72,7 @@ export const editMaintenanceByIdWindowBodyValidation = z
 		end: dateToString.optional(),
 		monitors: z.array(z.string()).optional(),
 		duration: z.number().optional(),
-		durationUnit: z.enum(["seconds", "minutes", "hours", "days"]).optional(),
+		durationUnit: z.enum(DurationUnits).optional(),
 	})
 	.strict()
 	.superRefine((data, ctx) => {