📊 feat: Google tag manager integration

[DenisPalnitsky]

Summary

Adds optional Google Tag Manager integration.
Discussion: #2430

Change Type

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Translation update
• Documentation update

Testing

Testing instructions (based on this article):

1. Copy .env.example to .env file
2. Uncomment ANALYTICS_GTM_ID in the .env file and set to to a valid Google Tag Manager account ID that has format similar to GTM-AAAAA123. You can enter random string there. In that case you won't see events in GTM but you still can test that functionality works.
3. Run backend and frontend
4. Load application and click around
5. In network tab you will see requests to gtm.js
   
6. Navigate to dev console and enter 'dataLayer' there. You should get list of events back
   
7. (optionally) Configure GTM account as described in GTM Set Up section here and verify that events are received by GTM.

Checklist

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• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• My changes do not introduce new warnings
• Local unit tests pass with my changes
• Any changes dependent on mine have been merged and published in downstream modules.