feat: Add new methods to list distinct mounts and retrieve all files in a mount

[marcelklehr]

Summary

These methods are needed for context chat and recognize to efficiently enumerate all files in the nextcloud instance.

In context chat and recognize we need to index all files of all users that fit certain criteria. To do this efficiently, we enumerate all essential mounts like home folders, external storage and groupfolders, excluding stuff like shares and trashbin. For this I implemented the getDistinctMounts method. It allows to filter by mount provider, so we can exclude shares etc. It also allows to adjust (override) home directory mounts to the actual files folder in a home directory, so we don't catch stuff that the user cannot see.

Once we have the distinct mounts, we enumerate all files non-recursively for each mount with getFilesByAncestorInStorage, it can filter by mimetypes and encryption state, and also takes a limit as well as a fileId cursor.

This is currently implemented in the context chat app, but as it makes use of the CacheQuery builder and core tables, the integrations team thinks it would be beneficial to have it in server.

Todo

• Tests

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[kyteinsky]

looks good!
just a few nits.

[julien-nc]

Not relying on OC stuff anymore in context_chat seems way better 👍
I can't say if those new methods are relevant but it looks like they could be used by other apps, in other contexts.

[marcelklehr]

Hey @skjnldsv@ArtificialOwl@skjnldsv Any of you perhaps willing to give this a review? It has already been reviewed by Anupam and Julien. I can walk you through the code in a meeting if that would help. It's an important step for our team's projects. Thanks!

[skjnldsv]

@marcelklehr I would ask for @sorbaugh to schedule a review call with fs experts such as Robin

[kyteinsky]

Marcel is on vacation, sent a ping to Stephan about this.

[marcelklehr]

Awesome. Tests in nextcloud/context_chat#142 pass