Add "open" button to instances with FQDN

closes #256

src/servala/frontend/templates/frontend/organizations/service_instance_detail.html

@@ -7,6 +7,15 @@
 {% endblock html_title %}
 {% block page_title_extra %}
     <div>
+        {% if instance.spec.parameters.service.fqdn %}
+            <a href="https://{{ instance.spec.parameters.service.fqdn.0 }}"
+               target="_blank"
+               rel="noopener noreferrer"
+               class="btn btn-success me-1 mb-1">
+                <i class="bi bi-box-arrow-up-right me-1"></i>
+                {% translate "Open" %}
+            </a>
+        {% endif %}
         {% if has_change_permission %}
             <a href="{{ instance.urls.update }}" class="btn btn-primary me-1 mb-1">{% translate "Edit" %}</a>
         {% endif %}