Short urls for sessions. (#1224)

pathname  /<session_code> redirects now to session
eg. https://ep2025-code.ep-preview.click/3BQFTP ->
https://ep2025-code.ep-preview.click/session/pyscript-as-infrastructure-running-edublocks-at-scale-without-the-cost/

Author: nikoshell

src/pages/[code].astro

@@ -0,0 +1,12 @@
+---
+import { getCollection } from "astro:content";
+export async function getStaticPaths() {
+  const sessions = await getCollection("sessions");
+  return sessions.map((entry) => ({
+    params: { code: entry.data.code },
+    props: { slug: entry.id},
+  }));
+}
+const { slug } = Astro.props;
+return Astro.rewrite(`/session/${slug}`);
+---

src/pages/session/[slug].astro

@@ -21,7 +21,7 @@ export async function getStaticPaths() {
 const sessions = await getCollection("sessions");
 
 const { entry } = Astro.props;
-
+const slug = entry.id;
 const speakers = await getEntries(entry.data.speakers);
 
 // Resolve session codes to session data
@@ -233,3 +233,12 @@ const nextSessionsOrdered = sameRoomNextSession
     </footer>
   </Section>
 </Layout>
+
+<script is:inline define:vars={{ slug }}>
+  const currentUrl = window.location.pathname;
+  const expectedUrl = `/session/${slug}`;
+
+  if (currentUrl !== expectedUrl) {
+    window.history.replaceState({}, '', expectedUrl);
+  }
+</script>