Fixed User login for non existing users (lookup().singleOrNull() isntead of .single())
DATAGRAPH-352/330 : Fixed issues relating to Sorting and Paging
DATAGRAPH-330 : Added test(although ignored) to highlight scenario where current fix does not work - i.e. use of function in Sort.Order
DATAGRAPH-330 : Used foreach and adjusted comment
DATAGRAPH-330 : Added missing @transactional annotations