implemented instance lists and pot, todos still missing

server/api/getAllMaintenanceVisitInstances.ts

@@ -0,0 +1,23 @@
+import { maintenanceVisitInstances, errorMsg } from "../middleware/maintenanceVisitInstances";
+import { OutgoingMessage } from 'http';
+
+export default defineEventHandler(async (event) => {
+
+    const headers: Record<string, Parameters<OutgoingMessage['setHeader']>[1]> = {
+        'Access-Control-Allow-Origin': 'https://tueitapp.tueit.de',
+        'Access-Control-Allow-Headers': 'authorization, content-type',
+        'Access-Control-Allow-Methods': 'GET,HEAD,PUT,PATCH,POST,DELETE',
+        'Access-Control-Allow-Credentials': 'true',
+    };
+    setResponseHeaders(event, headers)
+
+    if (!(errorMsg === '')) {
+        throw createError({
+            statusCode: 400,
+            statusMessage: errorMsg,
+        })
+    }
+
+    setResponseStatus(event, 200)
+    return maintenanceVisitInstances
+})