Optional OTLP export of request-level metrics (request and response-byte
counters keyed by route/status/conditional-GET, a duration histogram out
to 600s) plus server spans for slow or 5xx requests, nested under the
incoming W3C trace context. Off unless an OTLP endpoint or uptrace DSN is
configured; a config-less server is byte-for-byte unchanged.
Replace the placeholder README with the full public-facing README, and
switch licensing to BSD 3-Clause per aav's decision on ANW-28: add a single
LICENSE file, drop the dual LICENSE-MIT / LICENSE-APACHE, and update the
Cargo.toml license field to match. README/LICENSE content authored by kaa,
landed verbatim.
Assumed: dropping the old MIT/Apache files and updating Cargo.toml
license = BSD-3-Clause is the consistent completion of aav's BSD decision
(v0.0.0, nothing released relied on the old grant); flag if the dual
license was meant to stay.
