Activity Stream on Files: replace "remote user" with a uid relating to the link-share/email-share to improve transparency on changes

[jasond2020]

While working together with external people (not having a user account inside of the nc-instance), the traceability of who did changes are not given; in the acitivity stream only "remote user" is logged, regardless if the external person accessed the file from one or another link.

Technically it should be possible - at least for e-mail-shares - to have the mailadress in the activity stream if the change of a file was uploaded or done from this spefic link-url. Regarding "Link-Shares" there could be something like link#1 or part of the link-url - some uid, to have it traceable, who did the changes.

This could be relvant because of working policies or even be ISO-relevant inside of some working-environents and thus would be an argument not to use nextcloud at all.

Alternatives:
Guest-Accounts. But this is not really the same. It is not wanted to have a (possibly) countless number of external (restricted, guest-)user accounts inside of the nextcloud-instance - one is using link shares and email shares (especially the email shares) for people not having a user account, but who nontheless need (at least for a time) access to some files.