/// <summary>
            /// Initiates link up of an external user identifier with an existing customer.
            /// </summary>
            /// <param name="emailAddress">The email address where the activation token has been sent.</param>
            /// <param name="activationToken">Activation token (a GUID).</param>
            /// <param name="externalIdentityId">The external identity identifier.</param>
            /// <param name="externalIdentityIssuer">The external identity issuer.</param>
            /// <param name="customerId">The identifier for existing customer.</param>
            /// <returns>Result for linking external identity to an existing customer.</returns>
            public LinkToExistingCustomerResult InitiateLinkToExistingCustomer(string emailAddress, string activationToken, string externalIdentityId, string externalIdentityIssuer, string customerId)
            {
                CustomerDataManager dataManager = this.GetDataManagerInstance();

                return(dataManager.InitiateLinkToExistingCustomer(emailAddress, activationToken, externalIdentityId, externalIdentityIssuer, customerId));
            }