Write XMP sidecar files for external libraries to a separate directory

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request.

• Yes

The feature

I use an external library and I don't want immich (or anyone else !) to write files in the folders of my photos.
Immich currently writes sidecar .xmp files next to the original files.
I would like a setting to store sidecars for external libraries in a separate configurable directory (mirroring the folder structure or not, I don't care), so that original folders stay untouched, while metadata edits (description, tags, date, location) are still persisted as sidecars.

Platform

• Server
• Web
• Mobile