Greatly reduce repeated code

functions/api/inactivity/validate.ts

@@ -1,11 +1,4 @@
-function errorResponse(error: string, status = 400): Response {
-  return new Response(JSON.stringify({ error }), {
-    headers: {
-      "content-type": "application/json",
-    },
-    status,
-  });
-}
+import { jsonError } from "../../common.js";
 
 export default function (
   selectedDepartments: string[],
@@ -14,8 +7,7 @@ export default function (
   start: any,
   userDepartments?: string[],
 ): void | Response {
-  if (!userDepartments)
-    return errorResponse("Not part of any departments", 403);
+  if (!userDepartments) return jsonError("Not part of any departments", 403);
 
   if (
     !Array.isArray(selectedDepartments) ||
@@ -24,10 +16,10 @@ export default function (
     typeof reason !== "string" ||
     typeof start !== "string"
   )
-    return errorResponse("Invalid notice");
+    return jsonError("Invalid notice", 400);
 
   if (!selectedDepartments.every((dept) => userDepartments.includes(dept)))
-    return errorResponse(
+    return jsonError(
       "Cannot file an inactivity notice in a department you are not part of",
       403,
     );
@@ -45,5 +37,5 @@ export default function (
     startDate.getFullYear() > now.getFullYear() + 1 ||
     endDate.valueOf() < startDate.valueOf()
   )
-    return errorResponse("Dates are invalid");
+    return jsonError("Dates are invalid", 400);
 }