SecurityException : privilege 'Write' is not granted when copy/pasting a document, while the user only need ADD_CHILDREN

The user can create documents in the workspace through the UI, but not by copy/pasting, this is due to a permission check into the method AbstractSession.copy() : checkPermission(dstdoc, WRITE).
The user has the permissions ADD_CHILDREN, WRITE_PROPERTIES... but not WRITE.