use cookieretry only on presale event pages

src/pretix/presale/templates/pretixpresale/event/base.html

@@ -9,7 +9,7 @@
 {% load anonymize_email %}
 {% block thetitle %}
     {% if messages %}
-        {{ messages|join:" " }} :: 
+        {{ messages|join:" " }} ::
     {% endif %}
     {% block title %}{% endblock %}{% if request.resolver_match.url_name != "event.index" %} :: {% endif %}{{ event.name }}
 {% endblock %}
@@ -26,6 +26,7 @@
     {% if event.settings.google_site_verification %}
         <meta name="google-site-verification" content="{{ event.settings.google_site_verification }}" />
     {% endif %}
+    <script type="text/javascript" src="{% static "pretixpresale/js/csrfcookieretry.js" %}"></script>
     {{ block.super }}
 {% endblock %}
 {% block above %}

src/pretix/static/pretixpresale/js/csrfcookieretry.js

@@ -0,0 +1,13 @@
+document.addEventListener("DOMContentLoaded", () => {
+  const COOKIE_NAME = "__Host-pretix_csrftoken";
+  const RELOAD_FLAG = "csrfReloadPerformed";
+
+  const hasCookie = document.cookie
+    .split("; ")
+    .some((c) => c.startsWith(COOKIE_NAME + "="));
+
+  if (!hasCookie && !sessionStorage.getItem(RELOAD_FLAG)) {
+    sessionStorage.setItem(RELOAD_FLAG, "1");
+    location.reload();
+  }
+});