Fix: sheet export (#1606)

* add util to get keys from labels

* look for existing keys first then create new

* save ontime key to rundown metadata

* update test

packages/utils/src/customField-utils/customFieldLabelToKey.ts

@@ -1,3 +1,5 @@
+import type { CustomFields } from 'ontime-types';
+
 import { isAlphanumericWithSpace } from '../regex-utils/isAlphanumeric.js';
 
 /**
@@ -9,3 +11,11 @@ export const customFieldLabelToKey = (label: string): string | null => {
   }
   return null;
 };
+
+export const customKeyFromLabel = (label: string, fields: CustomFields): string | null => {
+  const maybeMatchingKey = Object.keys(fields).find((key) => fields[key].label === label);
+  if (maybeMatchingKey) {
+    return maybeMatchingKey;
+  }
+  return null;
+};