USWDS-Site - Feature: Add GA4 analytics snippet

[thisisdano]

Is your feature request related to a problem? Please describe.

We'll need to add a new code snippet to our websites so we can transition to GA4 data collection under the GSA Enterprise Analytics account while continuing to collect UA data on our existing account.

Describe the solution you'd like

The existing DAP code in _includes/analytics.html should continue to appear within the document head, but this new GA4 snippet AND our existing UA snippet should now appear directly after the head.

DAP implementation guide (PDF) → GA4 Implementation guide (see "Set up data collection for websites") →

In the head:

<--! DAP -->
<script async type="text/javascript" id="_fed_an_ua_tag" src="https://dap.digitalgov.gov/Universal-Federated-Analytics-Min.js?agency=GSA&subagency=TTS"></script>

Directly after head:

<--! GA4 -->
<!-- Google tag (gtag.js) --> <script async src="https://www.googletagmanager.com/gtag/js?id=G-HBYXWFP794"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-HBYXWFP794'); </script>

<--! UA -->
<script>
    window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
    ga('create', '{{ site.google_analytics_ua }}', 'gsa.gov');
    ga('send', 'pageview');
    // anonymize user IPs (chops off the last IP triplet)
    ga('set', 'anonymizeIp', true);

    // forces SSL even if the page were somehow loaded over http://
    ga('set', 'forceSSL', true);

    ga('send', 'pageview');
</script>
<script async src='https://www.google-analytics.com/analytics.js'></script>

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct.
• [X] I checked the current issues for duplicate feature requests.

[mahoneycm]

After reviewing the documentation, some Q&A online, and testing, I believe the instructions mean after the opening head tag rather than after the head completely / closing tag. More information available in #2428