fix: repair GTM injection

Author: themightychris

k8s.preprod/app-ingress.yaml

@@ -13,22 +13,13 @@ metadata:
     # allow requests larger than 1MiB
     nginx.ingress.kubernetes.io/proxy-body-size: "0"
     nginx.ingress.kubernetes.io/configuration-snippet: |
-      location / {
-      sub_filter </head>
-        '<!-- Google Tag Manager -->
-        <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
-        new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
-        j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
-        'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
-        })(window,document,'script','dataLayer','GTM-KBZ6ZKX');</script>
-        <!-- End Google Tag Manager -->';
-      sub_filter </body>
-        '<!-- Google Tag Manager (noscript) -->
-        <noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-KBZ6ZKX"
-        height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
-        <!-- End Google Tag Manager (noscript) -->'
-        sub_filter_once on;
-      }
+      # Inject Google Tag Manager:
+
+      proxy_set_header Accept-Encoding ""; # upstream compression must be disabled
+
+      sub_filter '</head>' '<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({"gtm.start": new Date().getTime(),event:"gtm.js"});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!="dataLayer"?"&l="+l:"";j.async=true;j.src="https://www.googletagmanager.com/gtm.js?id="+i+dl;f.parentNode.insertBefore(j,f); })(window,document,"script","dataLayer","GTM-KBZ6ZKX");</script></head>';
+
+      sub_filter '</body>' '<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-KBZ6ZKX" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript></body>';
 spec:
   tls:
   - hosts: