Merge branch '4.4' into 5.1

OskarStark · OskarStark · commit 43bfb3be0c97 · 2021-01-08T11:06:30.000+01:00
* 4.4:
  Add more details about the ESI detection
diff --git a/http_cache/esi.rst b/http_cache/esi.rst
@@ -156,9 +156,9 @@ used ``render()``.
 
 .. note::
 
-    Symfony detects if a gateway cache supports ESI via another Akamai
-    specification that is supported out of the box by the Symfony reverse
-    proxy.
+    Symfony considers that a gateway cache supports ESI if its responses include
+    the ``Surrogate-Capability`` HTTP header and the value of that header
+    contains the ``ESI/1.0`` string anywhere.
 
 The embedded action can now specify its own caching rules entirely independently
 of the master page::
