Sorting works incorrectly for some international characters with mongodb adapter

[wuron]

Describe the Bug

I'm developing an app in Ukrainian language and the sorting for some characters doesn't work as expected.
Having a posts collection with a single text field title, I'm trying to fetch them using local api:

const payload = await getPayload({ config });
const people = await payload.find({
  collection: 'posts',
  sort: ['title'],
});

The resulting documents are not sorted correctly.

I've seen a similar issue #6719 where it is suggested to change the mongo collation strength, but this doesn't resolve the issue, because the locale is just wrong.

I can get the documents with correct sorting using mongoose directly:

const documents = await payload.db.collections['posts'].find().sort('title').collation({
  locale: 'uk',
});

but the results are untyped and it feels like a hack using low level api for something that should work on high level.

I can see that payload.find accepts a locale param, but it doesn't change anything, and seems like it's used for i18n.
There's also a collation argument for mongooseAdapter but it does not accept locale.

Link to the code that reproduces this issue

https://github.com/payloadcms/payload

Reproduction Steps

1. Clone this repo and install dependencies. Basic template from reproduction guide is enough to reproduce this. No changes required.
2. run pnpm dev _community
3. Create 3 posts with the following titles: Роман, Віктор, Євген
4. Run a local query for posts sorted by title or open http://localhost:3000/api/posts?sort=title

Expected result: ["Віктор", "Євген", "Роман"]
Actual result: ["Євген", "Віктор", "Роман"]

Which area(s) are affected? (Select all that apply)

db-mongodb

Environment Info

Node: 22.13.0
payload: 3.21.0
next: 15.1.6

[paulpopus]

Hey, we have a PR in review for this but just note that you will need to apply collation config in your mongodb adapter for locale to be applied from locale: 'uk' within your queries.

At a minimum you will need this once the fix has gone out. We thread the locale from your request into the underlying queries

collation: {
      strength: 1,
    },