public async Task <bool> SavePhonebookAsync(CreatePhonebookCommand createPhonebookCommand)
        {
            Phonebook newPhonebook = new Phonebook()
            {
                Name = createPhonebookCommand.Name,
            };

            createPhonebookCommand.Entries.ForEach(e =>
            {
                Entry.Entry newEntry = new Entry.Entry
                {
                    Name        = e.Name,
                    PhoneNumber = e.PhoneNumber,
                };

                newPhonebook.Entries.Add(newEntry);
            });

            this._repository.Add(newPhonebook);

            return(await this._repository.SaveChanges().ConfigureAwait(false));
        }