public async Task DeleteMembers(string roleName, IEnumerable <string> usersId)
        {
            NullExpressionsExtensions.ThrowIfNull(roleName, () => new RoleNotFoundException("Role is null"));
            NullExpressionsExtensions.ThrowIfNull(usersId, nameof(usersId));

            AppRole role = await RoleManager.FindByNameAsync(roleName);

            if (role == null)
            {
                throw new RoleNotFoundException("There isn't role named " + roleName);
            }

            foreach (var user in usersId)
            {
                IdentityResult result = await IdentityManager.RemoveFromRoleAsync(user, role.Name);

                result.CheckResult();
            }
        }
        public async Task AddMembers(string roleName, IEnumerable <string> usersId)
        {
            NullExpressionsExtensions.ThrowIfNull(roleName, nameof(roleName));
            NullExpressionsExtensions.ThrowIfNull(usersId, nameof(usersId));

            if (usersId == null || !usersId.Any())
            {
                return;
            }

            AppRole role = await RoleManager.FindByNameAsync(roleName);

            if (role.Users.ToList().Select(x => x.UserId).Intersect(usersId).Any())
            {
                throw new UsersAreRecurringException("Users are recurring, no one were added.");
            }

            foreach (var user in usersId)
            {
                IdentityResult result = await IdentityManager.AddToRoleAsync(user, role.Name);

                result.CheckResult();
            }
        }