Fixes #39292 - Add cache HIT/MISS logging for Candlepin proxy caches

[pablomh]

Summary

Emit debug-level log lines via the :registration named logger for each cached Candlepin endpoint, enabling operators to verify cache effectiveness in production.

Log output (at debug level)

[registration] compliance cache=MISS uuid=abc123
[registration] compliance cache=HIT uuid=abc123
[registration] rhsm_status cache=MISS
[registration] rhsm_status cache=HIT

At the default info level, no additional log lines appear.

Dependencies

This is a draft PR that requires these PRs to merge first:

• Foreman #10946 — :registration named logger (Redmine #39290)
• Katello #11696 — Cache Candlepin status (Redmine #39204)

Will rebase onto master once dependencies are merged.

How to test

1. Enable debug logging in settings.yaml: :logging: :loggers: :registration: :level: debug
2. Register a host
3. Check production.log for cache=HIT and cache=MISS lines

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[jturel]

The HTTP requests (iirc) are all logged when the application is in debug mode so it's already easy to infer if there was a cache miss (http request logged) or a hit (no http request logged).

[pablomh]

The HIT/MISS logging uses the dedicated :registration logger from foreman#10946, which can be toggled independently without enabling debug for the entire application:

:logging:
  :loggers:
    :registration:
      :level: debug

So operators get cache observability by setting one logger to debug, not by running the whole application in debug mode.

[jturel]

Pausing my review here until #11692 reaches a resolution

[jturel]

• Needs rebase
• Compliance logging can be removed since we went a different route
• Recommend logging only cache misses since they're the exception and to keep log signal strength high

[pablomh]

I'll leave it in draft mode until theforeman/foreman#10946 is merged.