Keycloak login using IDP only

keycloak-scripts.json

{
    "authenticators": [
        {
            "name": "Identity Provider Selector",
            "fileName": "login-idp.js",
            "description": "(Guillaume Genty, 2025)"
        }
    ]
}

login-idp.ftl

<#import "template.ftl" as layout>
<@layout.registrationLayout displayMessage=!messagesPerField.existsError('username'); section>
    <#if section = "header">
        ${msg("loginAccountTitle")}
    <#elseif section = "socialProviders" >
        <#if realm.password && social?? && social.providers?has_content>
            <div id="kc-social-providers" class="${properties.kcFormSocialAccountSectionClass!}">
                <ul class="${properties.kcFormSocialAccountListClass!}">
                    <#list social.providers as p>
                        <a data-once-link data-disabled-class="${properties.kcFormSocialAccountListButtonDisabledClass!}" id="social-${p.alias}"
                                class="${properties.kcFormSocialAccountListButtonClass!}"
                                type="button" href="${p.loginUrl}">
                            <#if p.iconClasses?has_content>
                                <i class="${properties.kcCommonLogoIdP!} ${p.iconClasses!}" aria-hidden="true"></i>
                                <span class="${properties.kcFormSocialAccountNameClass!} kc-social-icon-text">${p.displayName!}</span>
                            <#else>
                                <span class="${properties.kcFormSocialAccountNameClass!}">${p.displayName!}</span>
                            </#if>
                        </a>
                    </#list>
                </ul>
            </div>
        </#if>
    </#if>

</@layout.registrationLayout>

login-idp.js

// Bindings: script, realm, user, session, authenticationSession, httpRequest, LOG

function authenticate(context) {
  var challenge = context.form().createForm("login-idp.ftl");
  context.challenge(challenge);
}