only cache response if response has cache-control header (#9885)

* only cache response if response has cache-control header

* add changeset

Author: psytrx

.changeset/tidy-worms-reflect.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+---
+
+fix: require explicit cache-control header for caching

packages/adapter-cloudflare/src/worker.js

@@ -55,7 +55,8 @@ const worker = {
 
 		// write to `Cache` only if response is not an error,
 		// let `Cache.save` handle the Cache-Control and Vary headers
-		return res.status >= 400 ? res : Cache.save(req, res, context);
+		pragma = res.headers.get('cache-control') || '';
+		return pragma && res.status < 400 ? Cache.save(req, res, context) : res;
 	}
 };