Form ajax

DEV-NOTES:

• Add the entry form-ajax to the file templates/layout/base.html.twig.

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• Add required fields in the file php/Api/Action/Form.php to validate whatever you want to (server-side validation).

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• Add files to /private/forms/ to load different data. DON'T forget to add the paths to the .gitignore file!
  The attribute <form action=""> must follow the following schema:
  /api/{route}/{path}[/ressource], e.g: /api/forms/newsletter/dummy (note that ressource is optional).
  

  Important: ressource can also be a form field (e.g.: <input type="hidden" name="ressource" value="dummy">) or part of the query (e.g.: ?ressource="dummy").
  If the GET parameter ressource is set, it will overwrite the value of the ressource in action.
  If the POST parameter ressource is set, it will overwrite the value of the ressource in action and the corresponding GET parameter (if set).
  

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• Add the attribute data-ajax="true" to the <form> to submit the form via ajax. BE

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• To edit the feedback messages, change the text in the file templates/partials/tmpl/form-ajax.html-twig. BE