Testing nominal case for the method findByName
adding tests and nominal test for the method olderThan
adding tests for Age difference method (olderThan)
feature implemented and linked to the main + small refactoring
Merge branch 'feature/UC/olderThan'

* feature/UC/olderThan:
  feature implemented and linked to the main + small refactoring
  adding tests for Age difference method (olderThan)
  adding tests and nominal test for the method olderThan
  Testing nominal case for the method findByName