[google-analytics] Preset clientId

Hi, in Google Analytics it is possible to preset the client id like this:

ga('create', 'UA-XXXXX-Y', 'auto', {
  'clientId': 'ourOwnDefinedId'
});

Sadly the Segment library does not allow customisations to this call. Having this option would help us a lot to tie everything together with server-side events. We generate an id per session and would like to pass this into GA as clientId.

The config for the create call is set up here:
https://github.com/segmentio/analytics.js-integrations/blob/79ae188cb3f0c0ef4c2178fd95cb7daae4a22639/integrations/google-analytics/lib/index.js#L123

Is there some precedence for programmatically passing options into analytics.js? My first thought was a global like:

const SEGMENT_GOOGLE_ANALYTICS_CLIENT_ID=<whatever custom logic I need to get it>;

Before the Segment snippet.

Segment support pointed me here from ticket 355364

Thanks! Let me know if you need more information.

Start in integrations/google-analytics/lib/index.js at the linked create-call configuration around line 123, and review how this integration accepts options. Determine how a caller could provide a custom Google Analytics clientId, then verify that the create call uses it without breaking existing configuration behavior.