Shared albums: add Share with... to the album context menu.

[ildyria]

1. On click Share with AJAX request the server to get the list of user with whom the album[s] [is/are] not shared with. Use the union to build the list:
   • A is not not shared with alice and bob,
   • B is not shared with bob and charlie.
   • => Selecting A, B will return the alice, bob, charlie
2. Display list, process is similar to move.

Require upload rights

[ildyria]

No to the share menu but via modal on the top. Good Enough for me.