Pyexasol

- Send `snapshotTransactionsEnabled` attribute only if set explicitly in connection option, prepare for Exasol 7.1 release.
- Default `snapshot_transaction` connection options is now `None` (database default), previously it was `False`.

- Added connection options `access_token` and `refresh_token` to support OpenID Connect in [WebSocket Protocol V3](https://github.com/exasol/websocket-api/blob/master/docs/WebsocketAPIV3.md).
- PyEXASOL default protocol version will be upgraded to `3` if connection option `access_token` or `refresh_token` were used.

- Fixed orphan process check in HTTP Transport being enabled on Windows instead of POSIX OS.

- Enforced TCP keep-alive for HTTP transport connections for Linux, MacOS and Windows. Keep-alive is required to address [Google Cloud firewall rules](https://cloud.google.com/compute/docs/troubleshooting/general-tips#communicatewithinternet) dropping idle connections after 10 minutes.

- Added INTERVAL DAY TO SECOND data type support for standard fetch mapper `exasol_mapper`. Now it returns instances of class `ExaTimeDelta` derived from Python [datetime.timedelta](https://docs.python.org/3/library/datetime.html#datetime.timedelta).

It may potentially cause some issues with existing code. If it does, you may define your own custom `fetch_mapper`. Alternatively, you may call `ExaTimeDelta.to_interval()` or cast the object to string to get back to original values.

- Added [`comment`](/docs/HTTP_TRANSPORT.mdparameters) parameter for HTTP transport. It allows adding custom SQL comments to EXPORT and IMPORT queries generated by HTTP transport query builders.