Attach documents to expenses (#64)

* Upload documents to receipts

* Improve documents

* Make the feature opt-in

* Fix file name issue

src/app/api/s3-upload/route.ts

@@ -0,0 +1,8 @@
+import { sanitizeKey } from 'next-s3-upload'
+import { POST as route } from 'next-s3-upload/route'
+
+export const POST = route.configure({
+  key(req, filename) {
+    return sanitizeKey(filename).toLowerCase()
+  },
+})