docs: fix broken links older GUC settings

No longer links but embeds the old settings in a details html element.

docs/references/transactions.rst

@@ -140,7 +140,36 @@ PostgREST stores the headers, cookies and headers as JSON. To get them:
 Legacy settings
 ^^^^^^^^^^^^^^^
 
-For PostgreSQL versions below 14, PostgREST will take into consideration the :ref:`db-use-legacy-gucs` config, which is set to true by default. This means that the interface for accessing these GUCs is `the same as in older versions <https://postgrest.org/en/v8.0/api.html#accessing-request-headers-cookies-and-jwt-claims>`_. You can opt in to use the JSON GUCs mentioned above by setting the ``db-use-legacy-gucs`` to false.
+For PostgreSQL versions below 14, PostgREST will take into consideration the :ref:`db-use-legacy-gucs` config, which is set to true by default.
+This means that the interface for accessing these GUCs is the same as in older versions (see below).
+You can opt in to use the JSON GUCs mentioned above by setting the ``db-use-legacy-gucs`` to false.
+
+.. raw:: html
+
+  <p>
+    <details>
+      <summary>Old GUCs</summary>
+
+.. code-block:: postgresql
+
+  -- To read the value of the User-Agent request header:
+  SELECT current_setting('request.header.user-agent', true);
+
+  -- To read the value of sessionId in a cookie:
+  SELECT current_setting('request.cookie.sessionId', true);
+
+  -- To read the value of the email claim in a jwt:
+  SELECT current_setting('request.jwt.claim.email', true);
+
+.. note::
+
+  ``request.jwt.claim.role`` defaults to the value of :ref:`db-anon-role`.
+
+.. raw:: html
+
+    </details>
+  </p>
+
 
 .. _guc_req_path_method: