NanoTimeSource

Injectable monotonic time, used exclusively for measuring the duration of an HTTP exchange.

Time is an injected dependency, not ambient state: the filter never calls System.nanoTime itself, so tests drive durations deterministically (typically from an AtomicLong). The values are monotonic nanoseconds with an arbitrary origin - only differences are meaningful, never wall-clock instants. Timestamps on the emitted log lines come from the logging backend, which keeps the two time domains separate by construction.