private async Task InitAuthors(IAuthorRepository authorRepository)
        {
            int authorsCount = await authorRepository.GetCount();

            if (authorsCount != 0)
            {
                return;
            }

            var authors = new List <Author>
            {
                new Author {
                    FirstName = "Taras", LastName = "Shevchenko"
                },
                new Author {
                    FirstName = "Lesya", LastName = "Ukrainka"
                },
                new Author {
                    FirstName = "Vasyl", LastName = "Symonenko"
                },
                new Author {
                    FirstName = "Oleksandr", LastName = "Dovzhenko"
                },
            };

            await authorRepository.AddRangeAsync(authors);
        }