I think I meant to make these changes over 6 months ago. alas, better
late than never.
1. should_reject doesn't eagerly intern the endpoint string
2. Rate limiter uses a std Mutex instead of a tokio Mutex.
3. Recently I introduced a `-local-proxy` endpoint suffix. I forgot to
add this to normalize.
4. Random but a small cleanup making the ControlPlaneEvent deser
directly to the interned strings.
The overall idea of the PR is to rename a few types to make their
purpose more clear, reduce abstraction where not needed, and move types
to to more better suited modules.
## Problem
Fixes#8340
## Summary of changes
Introduced ErrorKind::quota to handle quota-related errors
## Checklist before requesting a review
- [x] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
