public List <Formation> GetAllByCoach(Guid idCoach)
 {
     return(_context.Formation.Where(FormationSpecs.GetOneByCoach(idCoach)).ToList());
 }
 public Formation GetOneByCoach(Guid idCoach)
 {
     return(_context.Formation.Where(FormationSpecs.GetOneByCoach(idCoach)).FirstOrDefault());
 }