feat: Add basic redirect service

src/fellchensammlung/templates/fellchensammlung/details/detail_adoption_notice.html

@@ -50,7 +50,7 @@
                 {% if adoption_notice.further_information %}
                     <td>
                         <form method="get" action="{% url 'external-site' %}">
-                            <input type="hidden" name="url" value="adoption_notice.further_information">
+                            <input type="hidden" name="url" value="{{ adoption_notice.further_information }}">
                             <button class="btn" type="submit" id="submit">
                                  {{ adoption_notice.further_information | domain }} <i class="fa-solid fa-arrow-up-right-from-square"></i>
                             </button>

src/fellchensammlung/templates/fellchensammlung/external_site_warning.html

@@ -0,0 +1,10 @@
+{% extends "fellchensammlung/base_generic.html" %}
+{% load i18n %}
+{% block content %}
+    <div class="card">
+        {% blocktranslate %}
+            <p>Achtung du verlässt notfellchen.org</p>
+        {% endblocktranslate %}
+        <a href="{{ url }}" class="btn" >{% translate "Weiter" %}</a>
+    </div>
+{% endblock content %}