Check CI ID

`_generate_ci_id` generates a `group_id` field:

https://github.com/iterative/telemetry-python/blob/41bcc8717f461e5ad8555e10997299d755b19c83/src/iterative_telemetry/__init__.py#L333

DVC uses this function directly:

https://github.com/iterative/dvc/blob/e362438f03d1bc7b9c54d091e37bca72ef410cde/dvc/analytics.py#L109

However, the `group_id` field is always null in the DVC analytics. Need to investigate further.

Start at _generate_ci_id in src/iterative_telemetry/__init__.py around line 333, then compare its direct use in DVC's dvc/analytics.py around line 109. Trace why the generated group_id becomes null in DVC analytics; done means the cause is identified and the required correction is clearly established.

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