public interface IKeyedRepository<TKey, TEntity> : IRepository<TEntity> 
     where TEntity : class, IKeyed<TKey>
 {
    TEntity FindBy(TKey id);
 }
 public interface IRepository<TEntity> : IReadOnlyRepository<TEntity> where TEntity:class
 {
     bool Add(TEntity entity);
     bool Add(IEnumerable<TEntity> items);