Kinto-changes

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**Bug fixes**

- Use explicit resource timestamp from DB instead of event payload

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**New feature**

- Send ``Cache-Control`` headers if cache busting query parameters or concurrency control request headers are sent (66)

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**Breaking changes**

- Requires Kinto >= 12

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**New feature**

- Add ability to configure cache control headers (47)

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**Bug fixes**

- Don't do anything during a ``migrate`` command (fixes 43).

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**New feature**

- Events are now generated on the monitor/changes collection (41).