fix: case-insensitive author merge check on rename

When renaming an author from e.g. 'max' to 'Max', the merge
check now uses case-insensitive comparison (Op.iLike) instead of
exact match. Previously, if an author named 'Max' already existed,
renaming 'max' to 'Max' would not find the existing author because
the comparison was case-sensitive. This caused duplicate authors
with the same name but different cases.

Fixes #5278

server/controllers/AuthorController.js

@@ -121,7 +121,9 @@ class AuthorController {
           id: {
             [sequelize.Op.not]: req.author.id
           },
-          name: payload.name,
+          name: {
+            [sequelize.Op.iLike]: payload.name
+          },
           libraryId: req.author.libraryId
         }
       })