When we're in Sidekiq, in most cases we want to use the feature category
of the current worker class in logs and metrics. If a worker with the
'users' feature category is called by an endpoint that has the
'issue tracking' feature category, then 'users' is the more specific
category.

However, for workers without an owning feature category, this is worse:
we're effectively throwing away the information from the surrounding
context to give the least-specific information we could possibly give.
This changes that so that in logs and in metrics, we'll use the feature
category from the calling context for workers that don't have an owner.