public static async Task Initialize(AppDbContext context, UserManager <IdentityUser> userManager,
                                            RoleManager <IdentityRole> rolesManager)
        {
            context.Database.EnsureCreated();

            var identityRoles = new string[] { "Admin", "Operator", "User" };
            var identityUsers = new IdentityUser[]
            {
                new IdentityUser()
                {
                    UserName = "******", Email = "*****@*****.**"
                },
                new IdentityUser()
                {
                    UserName = "******", Email = "*****@*****.**"
                },
                new IdentityUser()
                {
                    UserName = "******", Email = "*****@*****.**"
                },
            };
            var password = "******";

            foreach (var role in identityRoles)
            {
                if (!await rolesManager.RoleExistsAsync(role))
                {
                    await rolesManager.CreateAsync(new IdentityRole(role));
                }
            }

            foreach (var identityUser in identityUsers.Select((value, i) => new { i, value }))
            {
                if (await userManager.FindByNameAsync(identityUser.value.UserName) == null)
                {
                    var result = userManager.CreateAsync(identityUser.value).Result;

                    if (result.Succeeded)
                    {
                        await userManager.AddPasswordAsync(identityUser.value, password);

                        await userManager.AddToRoleAsync(identityUser.value, identityRoles[identityUser.i]);
                    }
                }
            }
        }