## Summary
Add a new `circuit_breaker_thresholds` option:
```yaml
circuit_breaker_thresholds:
max_connections: 1
max_pending_requests: 2
max_requests: 3
max_retries: 4
max_connection_pools: 5
```
This option can be set at the global level or at the route level. Each
threshold is optional and when not set a default will be used. For
internal clusters we will disable the circuit breaker. For normal routes
we will use the envoy defaults.
## Related issues
-
[ENG-2310](https://linear.app/pomerium/issue/ENG-2310/add-circuit-breaker-settings-per-route)
## Checklist
- [x] reference any related issues
- [x] updated unit tests
- [x] add appropriate label (`enhancement`, `bug`, `breaking`,
`dependencies`, `ci`)
- [x] ready for review
