[Feature] Merge person properties when missing

[daniele-athome]

The feature

Today, if you merge person A into person B, person A having a name and person B having not one, person A's name would be lost. It would be nice if properties that are missing on the destination person would be filled from the source person - with a proper notice to the user of course.

This can be prevented by reverting the merge (merge B into A), but maybe I'm already on person A's page and that's faster, or maybe I bumped into the 500 people limit of the API so I can only see person A and start the merge from there.

This is particularly relevant since the addition of date of birth in #3721 (date of birth follows the same principle as for the name).

Platform

• Server
• Web
• Mobile