Clean-python

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- Added `S3Gateway.remove_filtered`.

- Added `clean_python.s3.KeyMapper`.

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- Adapt `InternalGateway` so that it derives from `Gateway`.

- Renamed the old `InternalGateway` to `TypedInternalGateway`.

- Added `SQLDatabase.truncate_tables()`.

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- Added `InternalGateway.update`.

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- Support adding/changing `responses` via route_options.

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- Added optional bind parameters for `execute` in `SQLProvider`,
`SQLDatabase` and `SQLTransaction`.

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- Don't use environment variables in setup_debugger.

- Add Id type (replaces int), it can also be a string.

- Added S3Gateway.

- Reinstate static type linter (mypy).