private static AzureUserReference CreateEmailReference(TUser user)
        {
            if (String.IsNullOrEmpty(user.NormalizedEmail))
            {
                return(null);
            }

            var referenceKey = AzureUserReferenceKey.ForEmail(user.NormalizedEmail);

            return(new AzureUserReference(referenceKey, user.Id)
            {
                ETag = "*"
            });
        }
        public async Task <TUser> FindByEmailAsync(string normalizedEmail, CancellationToken cancellationToken)
        {
            var referenceKey = AzureUserReferenceKey.ForEmail(normalizedEmail);

            return(await this.GetUserByReference(referenceKey));
        }