refact: avoid mem alloc for debug log

[regeda]

Each check request creates unnecessary memory garbage for the debug message, even when the log level is set higher than debug.

Benchmark results.

goos: darwin
goarch: arm64
pkg: github.com/open-policy-agent/opa-envoy-plugin/internal
cpu: Apple M2 Pro

With Debug:

BenchmarkCheck-12            15576             78914 ns/op           54843 B/op       1088 allocs/op

Without Debug:

BenchmarkCheck-12            16891             75411 ns/op           51540 B/op       1037 allocs/op

[anderseknert]

Thanks! Can't we just wrap that call in a check for log level? The information may be available elsewhere, but if anyone expects to find it there with debug logging turned on, it'd be good if they still found it.

[regeda]

Thanks! Can't we just wrap that call in a check for log level? The information may be available elsewhere, but if anyone expects to find it there with debug logging turned on, it'd be good if they still found it.

Agree. I've wrapped the log statement with a condition.