AuthorshipEntity: Adjust to DB schema

This commit replaces the user property with a author property,
in accordance with the DB schema updated in 0d6c3002.

It also adjusts the NoteService accordingly.

Signed-off-by: David Mehren <git@herrmehren.de>

src/notes/notes.service.ts

@@ -310,7 +310,7 @@ export class NotesService {
       // the user of that Authorship is the updateUser
       return lastRevision.authorships.sort(
         (a, b) => b.updatedAt.getTime() - a.updatedAt.getTime(),
-      )[0].user;
+      )[0].author.user;
     }
     // If there are no Authorships, the owner is the updateUser
     return note.owner;