Assigning a resources to an observatory updates the user
I am not sure if it is a back-end issue, so we should investigate it first: When assigning a paper or comparison to an observatory (as curator), the "created_by" field gets updated to the current user. So effectively, the user making the assignment "takes over" the contributions. This part of the metadata should be kept intact.
If re-assignment to a different user is needed, we should properly support that.