[Feature] Write face metadata to sidecar files

[bo0tzz]

I have searched the existing feature requests to make sure this is not a duplicate request.

• Yes

The feature

After a face is detected in an image, write it back to the file metadata so it's persisted outside of Immich's internal database.

cont. #4348

Platform

• Server
• Web
• Mobile

[grunwalski]

I do think this is an feature many people don't think about ahead and therefore will not request activley. But I'd also guess, many people would miss it, once they realize, their downloaded photos are missing some bits - literally.

For me, trying immich its about getting away from google or apple photos, who already don't allow me to move ALL my data at once. I really wouldn't like to have another captor.

Being able to write generated metadata into the files or an XMP sidecar feels like a net I didnt expect when fell. Its about wanting to be here, because I could leave, not because moving would be a hassle. :)

[cbbyrnes4]

there may already be another issue for this, but I think it'd be great to give the user the option to write the metadata, through Immich, to the photo files directly (as opposed to the sidecar files). That way everything is self-contained, and you don't run the risk of those files being separated at some point. I do understand the philosophy of keeping them separate so as not to "taint" the originals, but a choice would be great.