public async Task AuthenticateExternalAsync(ExternalAuthenticationContext context)
{
var externalIdentity = Mapper.Map <IdentityServerExternalIdentity, DomainExternalIdentity>(context.ExternalIdentity);
var signInData = Mapper.Map <SignInMessage, SignInData>(context.SignInMessage);
var result = await domainService.AuthenticateExternalAsync(externalIdentity, signInData);
context.AuthenticateResult = Mapper.Map <AuthenticationResult, AuthenticateResult>(result);
}