Feature: #84650 - Introduce fluid data processor for language menus

See Issue #84650

Description

This feature introduces a new LanguageMenuProcessor for Fluid based language menus based on the languages defined for the current site.

Options

if : TypoScript if condition
languages : A list of comma separated language IDs (e.g. 0,1,2) to use for the menu creation or auto to load from site languages
as : The variable to be used within the result

Example TypoScript configuration

10 = TYPO3\CMS\Frontend\DataProcessing\LanguageMenuProcessor
10 {
   languages = auto
   as = languageNavigation
}

Example Fluid-Template

<f:if condition="{languageNavigation}">
   <ul id="language" class="language-menu">
      <f:for each="{languageNavigation}" as="item">
         <li class="{f:if(condition: item.active, then: 'active')}{f:if(condition: item.available, else: ' text-muted')}">
            <f:if condition="{item.available}">
               <f:then>
                  <a href="{item.link}" hreflang="{item.hreflang}" title="{item.navigationTitle}">
                     <span>{item.navigationTitle}</span>
                  </a>
               </f:then>
               <f:else>
                  <span>{item.navigationTitle}</span>
               </f:else>
            </f:if>
         </li>
      </f:for>
   </ul>
</f:if>