[Bug] Recent activity feed misattributes changes to volume owner

[BNAndras]

Describe the problem
In the recent activity feed, changes to a document or layer are attributed to the volume owner even if they were done by someone else.

Expected behavior
Changes to documents and layers should be attributed to the registered user who performed the operation (e. g. splitting an operation or georeferencing a layer).

[mradamcox]

This wasn't a bug, per se, but it definitely warrants revisiting. Who should be the "owner" of a document when it is prepared? What does the "owner" property mean, anyway? It would be best to address the latter question first. We can always present the name of who prepared a document without changing the "owner" attribute.