[REFACTOR] Use Convenient Naming Convention for repo Package

[mohamed-sallam]

Use cleaner code style as suggested in Clean Code By Uncle Bob.

These are sometimes a special case for encodings. For example, say you are building an
ABSTRACT FACTORY for the creation of shapes. This factory will be an interface and will
be implemented by a concrete class. What should you name them? IShapeFactory and
ShapeFactory? I prefer to leave interfaces unadorned. The preceding I, so common in
today’s legacy wads, is a distraction at best and too much information at worst. I don’t
want my users knowing that I’m handing them an interface. I just want them to know that
it’s a ShapeFactory. So if I must encode either the interface or the implementation, I choose
the implementation. Calling it ShapeFactoryImp, or even the hideous CShapeFactory, is pref-
erable to encoding the interface.
-- Uncle Bob

So replace GroupRepository with GroupRepositoryImpl and IGroupRepository with GroupRepository.