Add username label in shared album for added photos

[Phils80]

When I'm using shared albums I'm missing information who is owner of the photo, or if preffered who added photo to album. Simply I don't like to use somebody else's photo as my own and then provoke any misunderstandings between users sharing photos in one album.

I would like to have possibility of turning on photos labelling on preview and / or sorting by user / owner.

Now I need to enter "info" and the only thing I can do is to check camera type, sometimes I can find out if it is my photo or I recieved it from somebody, but it is quite frustrating and not effective way.

Similar feature exist in Google Photos, please find photo below:

[jovanbulck]

I find this feature really lacking when sharing large albums and/or timelines with multiple people, so I had a shot at implementing this the other day. Currently looks as follows:

The nextcloud username is shown in the bottom left of the picture frame for all pictures that are not owned by the logged-in user, both in the Timeline and Albums view.

The added ownership information should also make it easy to implement #787 -- one of the only features that Photos has that Memories doesn't..

Current support is minimal (feedback welcome), but I'll open a PR shortly for implementation-specific discussion.