UserID Field Migration Catch-All

I see you, you pesky, duplicated fields and values in our logs. I'm coming to get you!

The aim for this task is to ensure that ALL logs that contain some form of user_id field/value in their logs are additionally emitting the new gl_user_id field with the value appropriately populated.

This will then allow us to start removing the non-standard fields in a fairly straightforward and safe manner.

Service Status

Service Name	Status	Notes
customers-gitlab-com	Migrated	https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/13677 - once this has landed, we should have the vast majority of places emitting this new field. We can then check to see if other places need this to be added.
gitlab	Merged	Adds the gl_user_id field to the application_context** -** has been raised, waiting on feedback from Bob to ensure we're aligned. This will hopefully mean the vast majority of logs should start emitting this. I can then start chipping away at the inconsistent fields once this has landed.

Outcome

The outcome of this ticket isn't to simply do the migration, but rather to uncover any difficulties that may be experienced in attempting to bring about standardisation in other fields as we continue to address this problem.