Add landing page test

This guards against any future refactor accidentally leaving a raw
{{VERSION}} or {{COMMIT}} in the response.

Co-authored-by: carlos santos <rickhenriquetab@gmail.com>

Author: spacebear21

payjoin-mailroom/src/directory.rs

@@ -793,4 +793,13 @@ mod tests {
         assert_eq!(status, StatusCode::OK);
         assert_eq!(body, r#"{"versions":[1,2]}"#);
     }
+
+    // Landing page
+
+    #[test]
+    fn landing_page_contains_version() {
+        let html = landing_page_html();
+        assert!(!html.contains("{{VERSION}}"));
+        assert!(!html.contains("{{COMMIT}}"));
+    }
 }