New private document set in private collection gets unrelated owner

[bencomp]

In our installation, I am the admin. For testing, I created a private collection a long time ago and for further testing I recently created a private document set within that collection. Upon submitting the information, my "test set" has a completely different owner, who cannot access the collection or the document set – I verified this by logging in as them.

I reported this in #2075 and added this comment to #3298:

It turns out I did not understand the idea of staff accounts. It sounds like "staff" is a role within an organisation account, but in our installation my (admin) account is a staff account that is not strictly linked to another account. @benwbrum pointed to this issue because a private document set that I created in my own private collection suddenly had a completely different owner who has no relation with or access to my private collection. I traced that behaviour back to #2075, from which I learned that staff accounts are special.

Originally posted by @bencomp in https://github.com/benwbrum/fromthepage/issues/3298#issuecomment-2449286183

[bencomp]

Edited: There is no connection with #1763.