Svix

* Server: include idempotency key in log spans.
* Server: correct trace ID handling in tracing spans.

* Server: add unique IDs when tracing worker tasks.
* Server: allow enabling extra tracing for db operations.
* Server: ensure tracing spans are recorded for all log levels.
* Server: reduce idempotency key lock time from 20s to 5s.
* Libs: expose endpoint stats function.

* Server: fix validation errors to be more informative.
* Server: more strict message payload validation to match the libs.
* Server: fix issue with messages being signed with expired keys in some situations (not a security concern, just superfluous data being sent).
* Server: attach a unique ID to a request (used in logs) when none is provided in headers.
* Libs/Python: fix typo in Python lib causing auto-detection of EU servers to fail.
* Libs/C: make logger optional when creating SvixClient.

* Server: support "upsert" of entities on PUT methods.
* Server: support PATCH methods on entities for partial updates.
* Server: allow overriding redis_dsn for separate queue and cache DSNs.
* Libs: support "upsert" of entities on PUT methods.
* Libs/Ruby: fix region auto-detection.

* Server: change the dashboard authentication payload to note that the server is self hosted.
* Libs/JavaScript: fix issue when signing/verifying payloads with high Unicode codepoints (e.g. some new emoji)

* Libs/Go: export missing `svix.NullableString` utility.