feat: make the language dropdown items set the language cookie

Include i18n urls then add a form to set the cookie using the currently implemented items

wger/core/templates/tags/language_select.html

@@ -1,11 +1,11 @@
 {% load i18n static %}
 
 <li>
-    <a class="dropdown-item" href="{{ i18n_path }}">
+    <button class="dropdown-item" type="button" data-language="{{ code }}">
         <img src="{% static path %}"
              width="20"
              alt="{% translate name %}"
              title="{% translate name %}">
         {% translate name %} / <small>{{ name }}</small>
-    </a>
+    </button>
 </li>

wger/core/templates/template.html

@@ -203,15 +203,32 @@
                         </button>
 
                         <ul class="dropdown-menu language-menu" aria-labelledby="btnGroupLanguages">
+
                             <li>
                                 <a href="" class="dropdown-item">
                                     <span class="{% fa_class 'globe' %}"></span>
                                     <span>{% translate "Browser language" %}</span>
                                 </a>
                             </li>
-                            {% for language in languages %}
-                                {% language_select language %}
-                            {% endfor %}
+
+                            <form id="language-form" action="{% url 'set_language' %}" method="post">
+                                {% csrf_token %}
+                                <input name="next" type="hidden" value="{{ redirect_to }}">
+                                <input type="hidden" name="language" id="language-input">
+                                {% for language in languages %}
+                                    {% language_select language %}
+                                {% endfor %}
+                            </form>
+                            <script>
+                                document.querySelectorAll('[data-language]').forEach(item => {
+                                    item.addEventListener('click', function(e) {
+                                        e.preventDefault();
+                                        document.getElementById('language-input').value = this.dataset.language;
+                                        document.getElementById('language-form').submit();
+                                    });
+                                });
+                            </script>
+
                             <li>
                                 <hr class="dropdown-divider"></hr>
                             </li>

wger/urls.py

@@ -297,6 +297,7 @@ urlpatterns = i18n_patterns(
 # URLs without language prefix
 #
 urlpatterns += [
+    path("i18n/", include("django.conf.urls.i18n")),
     path('robots.txt', TextTemplateView.as_view(template_name='robots.txt'), name='robots'),
     # API
     path('api/v2/exercise/search/', exercises_api_views.search, name='exercise-search'),