As a Conifer dev user, I want to consume a DimissableAlert class

[acobster]

A workable implementation of this exists in WSHS in the Alert\DismissableAlert class.

Expected behavior

I should be able to set an alert in the Timber context:

      $context['global_alert'] = new DismissableAlert($message, [
        'cookies' => $_COOKIE,
      ]);

Then consume it like this in Twig:

{% if global_alert and not global_alert.dismissed %}
<script>
    window.addEventListener('DOMContentLoaded', function() {

        var bar = document.querySelector('.site-alert'),
            closeBtn = bar.querySelector('.site-alert__close');

    closeBtn.addEventListener('click', function(e) {
      e.preventDefault();
      // hide the alert bar
      bar.style.display = 'none';
      // persist the dismissal in a cookie
      document.cookie = closeBtn.dataset.alertCookie;
    });
    });
</script>

<div class="site-alert">
  <div class="site-alert__wrapper container">

    <div class="site-alert__text rtecontent">
      {{ global_alert.message }}
      <a href="#"
         data-alert-cookie="{{ global_alert.cookie_text }}"
         class="site-alert__close">{{ source('img/icons/icon-close.svg') }}<span class="screen-reader-text">Close</span></a>
    </div>

  </div>
</div>

{% endif %}

Actual behavior

It ain't work like that.

TODO

• [x] backport this class to Conifer
• [x] write some tests