@GET
    @Path("login")
    public Response redirectToIdentityProvider() throws GuacamoleException {
        return Response.seeOther(authService.getLoginURI()).build();
    }
Redirects the user to the relevant identity provider. If the SSO
extension defining this resource is not the primary extension, and thus
the user will not be automatically redirected to the IdP, this endpoint
allows that redirect to occur manually upon a link/button click.

@return
    An HTTP Response that will redirect the user to the IdP.

@throws GuacamoleException
    If an error occurs preventing the redirect from being created.
extensions/guacamole-auth-sso/modules/guacamole-auth-sso-base/src/main/java/org/apache/guacamole/auth/sso/SSOResource.java