Add infos.json based on main event infos

This commit adds an auto-generated `infos.json` to our website based on
information provided in the `settings.py`.
These infos are now also used to fill some infos on the website.

settings.py

+import datetime
 import os
+import json
 import flamingo
+from flamingo.core.context import Context
+from flamingo.core.data_model import Content, ContentSet
+from flamingo.core.templating import TemplatingEngine
+
+# Event Core Infos
+EVENT_INFO = {
+    "next": {
+        "start": "2025-07-01",
+        "end": "2025-07-05",
+        "event": "Hacken Open Air 2::25",
+        "location_city": "Gifhorn",
+    }
+}
 
 THEME_PATHS = [
         'theme/',
@@ -30,3 +45,20 @@ def fix_headings(context):
 POST_BUILD_LAYERS = [
         'downloads',
 ]
+
+@flamingo.hook("templating_engine_setup")
+def event_info_templates(_context: Context, templating_engine: TemplatingEngine):
+    """Add the Event-Info to the template context."""
+
+    start = datetime.date.fromisoformat(EVENT_INFO["next"]["start"])
+    end = datetime.date.fromisoformat(EVENT_INFO["next"]["end"])
+
+    templating_engine.env.globals["EVENT_HEADLINE"] = EVENT_INFO["next"]["event"]
+    templating_engine.env.globals["EVENT_TAGLINE"] = \
+        f"{start.strftime('%d.%m.')} - {end.strftime('%d.%m.%Y')} in {EVENT_INFO['next']['location_city']}"
+
+@flamingo.hook("contents_parsed")
+def event_info_json(context: Context):
+    """Write the event info as infos.json into the output."""
+    contents: ContentSet = context.contents
+    contents.add(Content(output="infos.json", content_body=json.dumps(EVENT_INFO), path=""))

theme/templates/base.html

@@ -6,7 +6,7 @@
     <meta property="og:image" content="https://hackenopenair.de/media/pool.jpeg">
     <link rel="icon" href="./static/img/favicon.png" type="image/png">
     <title>
-            {% block title %}Hacken Open Air 2::25{% endblock %}
+            {% block title %}{{ EVENT_HEADLINE }}{% endblock %}
     </title>
     <link rel="stylesheet" href="./static/css/hoa.css">
   </head>

theme/templates/page.html

@@ -4,7 +4,7 @@
 <header>
     <div id="top"></div>
     <div class="headers">
-        <h1>Hacken Open Air 2::25</h1>
+        <h1>{{ EVENT_HEADLINE }}</h1>
     </div>
 </header>
 <aside>
@@ -32,7 +32,7 @@
 <div class="main">
     <article>
         <div align="center">
-            <h3>01.07 bis 05.07.2025 in Gifhorn</h3>
+            <h3>{{ EVENT_TAGLINE }}</h3>
             <img id="specht" src="./static/img/specht.svg" alt="logo">
         </div>
         {{ content.content_body }}