File extension of resources must be lower cased
When uploading a resource with upper case characters in the file extension (for instance "SomeFile.JPG") the saved persistent resource will be saved with a lower cased file extension ("<hash>.jpg"). This is correct, because it avoids clashes for two files with the same content (= same hash).
Resource::getFileExtension() already returns the lowercased extension,
Resource::getFilename() does not yet.