How to send additional parameters in keycloak login?

I am working on keycloak login and I have to send additional parameters in keycloak login such as role to login as admin and a normal user. I would like to know is it possible. I have added a checkbox for admin in login template. I attach the template of login theme below. If someone knows how about it then please let me know. Thank you.

login.ftl

<#import "template.ftl" as layout>
<@layout.registrationLayout displayMessage=!messagesPerField.existsError('username','password') displayInfo=realm.password && realm.registrationAllowed && !registrationDisabled??; section>
    <#if section = "header">
        ${msg("loginAccountTitle")}
    <#elseif section = "form">
    <div id="kc-form">
      <div id="kc-form-wrapper">
        <#if realm.password>
            <form id="kc-form-login" onsubmit="login.disabled = true; return true;" action="${url.loginAction}" method="post">
                <#if !usernameHidden??>
                    <div class="${properties.kcFormGroupClass!}">
                        <label for="username" class="${properties.kcLabelClass!}"><#if !realm.loginWithEmailAllowed>${msg("username")}<#elseif !realm.registrationEmailAsUsername>${msg("usernameOrEmail")}<#else>${msg("email")}</#if></label>

                        <input tabindex="1" id="username" class="${properties.kcInputClass!}" name="username" value="${(login.username!'')}"  type="text" autofocus autocomplete="off"
                               aria-invalid="<#if messagesPerField.existsError('username','password')>true</#if>"
                        />

                        <#if messagesPerField.existsError('username','password')>
                            <span id="input-error" class="${properties.kcInputErrorMessageClass!}" aria-live="polite">
                                    ${kcSanitize(messagesPerField.getFirstError('username','password'))?no_esc}
                            </span>
                        </#if>

                    </div>
                </#if>

                <div class="${properties.kcFormGroupClass!}">
                    <label for="password" class="${properties.kcLabelClass!}">${msg("password")}</label>

                    <input tabindex="2" id="password" class="${properties.kcInputClass!}" name="password" type="password" autocomplete="off"
                           aria-invalid="<#if messagesPerField.existsError('username','password')>true</#if>"
                    />

                    <#if usernameHidden?? && messagesPerField.existsError('username','password')>
                        <span id="input-error" class="${properties.kcInputErrorMessageClass!}" aria-live="polite">
                                ${kcSanitize(messagesPerField.getFirstError('username','password'))?no_esc}
                        </span>
                    </#if>

                </div>

                <div class="${properties.kcFormGroupClass!}">
                    <div class="checkbox">
                        <label><input type="checkbox" id="admin" name="admin" value="on"> Admin mode </label>
                    </div>
                </div>

                <div class="${properties.kcFormGroupClass!} ${properties.kcFormSettingClass!}">
                    <div id="kc-form-options">
                        <#if realm.rememberMe && !usernameHidden??>
                            <div class="checkbox">
                                <label>
                                    <#if login.rememberMe??>
                                        <input tabindex="3" id="rememberMe" name="rememberMe" type="checkbox" checked> ${msg("rememberMe")}
                                    <#else>
                                        <input tabindex="3" id="rememberMe" name="rememberMe" type="checkbox"> ${msg("rememberMe")}
                                    </#if>
                                </label>
                            </div>
                        </#if>
                        </div>
                        <div class="${properties.kcFormOptionsWrapperClass!}">
                            <#if realm.resetPasswordAllowed>
                                <span><a tabindex="5" href="${url.loginResetCredentialsUrl}">${msg("doForgotPassword")}</a></span>
                            </#if>
                        </div>

                  </div>

                  <div id="kc-form-buttons" class="${properties.kcFormGroupClass!}">
                      <input type="hidden" id="id-hidden-input" name="credentialId" <#if auth.selectedCredential?has_content>value="${auth.selectedCredential}"</#if>/>
                      <input tabindex="4" class="${properties.kcButtonClass!} ${properties.kcButtonPrimaryClass!} ${properties.kcButtonBlockClass!} ${properties.kcButtonLargeClass!}" name="login" id="kc-login" type="submit" value="${msg("doLogIn")}"/>
                  </div>
            </form>
        </#if>
        </div>

    </div>
    <#elseif section = "info" >
        <#if realm.password && realm.registrationAllowed && !registrationDisabled??>
            <div id="kc-registration-container">
                <div id="kc-registration">
                    <span>${msg("noAccount")} <a tabindex="6"
                                                 href="${url.registrationUrl}">${msg("doRegister")}</a></span>
                </div>
            </div>
        </#if>
    <#elseif section = "socialProviders" >
        <#if realm.password && social.providers??>
            <div id="kc-social-providers" class="${properties.kcFormSocialAccountSectionClass!}">
                <hr/>
                <h4>${msg("identity-provider-login-label")}</h4>

                <ul class="${properties.kcFormSocialAccountListClass!} <#if social.providers?size gt 3>${properties.kcFormSocialAccountListGridClass!}</#if>">
                    <#list social.providers as p>
                        <a id="social-${p.alias}" class="${properties.kcFormSocialAccountListButtonClass!} <#if social.providers?size gt 3>${properties.kcFormSocialAccountGridItem!}</#if>"
                                type="button" href="${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>