feat(google-tag-web): send (authenticated) user ID

[rborer]

Pull request type

New feature (non-breaking change which adds functionality)

Description

This change introduce a new functionality allowing to optionally share the authenticated user ID with Google Analytics.

Sharing this information allow Google Analytics to identify individual users across different sessions and devices.

This is achieved by modifying the config command to add the new user_id parameter.

For more details on the feature, please have a look at https://developers.google.com/analytics/devguides/collection/ga4/user-id?client_type=gtag .

[rborer]

To give more context, here is how it looks like when we use a GA debugger browser extension:

turned off (the default)

turned on