Update CHANGELOG (#846)

Co-authored-by: api-clients-generation-pipeline[bot] <54105614+api-clients-generation-pipeline[bot]@users.noreply.github.com>

Author: api-clients-generation-pipeline[bot]

CHANGELOG.md

@@ -1,5 +1,27 @@
 # Changelog
 
+## 1.9.0 / 2022-02-17
+
+### Fixed
+* Add missing type to `CloudWorkloadSecurityAgentRuleAttributes` by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/841
+### Added
+* Add organization metadata to additional Usage API responses by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/809
+* Add support for formula and function in monitors by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/815
+* Add endpoint for managing SAML AuthN mappings by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/813
+* [Synthetics] Add `isCritical` to browser test steps by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/826
+* Add metrics bulk-config endpoint by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/818
+* Add support for "estimated usage attribution" by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/839
+* Add org metadata for all hourly usage endpoints by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/843
+### Changed
+* Add CSPM usage fields and change properties to nullable doubles by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/795
+* Add synthetics test result failure field by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/811
+* Fix funnel steps definition by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/832
+* Store unknown model properties in `_data_store` map by @therve in https://github.com/DataDog/datadog-api-client-python/pull/837
+* Extract incident meta object by @api-clients-generation-pipeline in https://github.com/DataDog/datadog-api-client-python/pull/838
+
+
+**Full Changelog**: https://github.com/DataDog/datadog-api-client-python/compare/1.8.0...1.9.0
+
 ## 1.8.0 / 2022-01-20
 
 * [Added] Add `filter[deleted]` parameter for searching recently deleted dashboards. See [#787](https://github.com/DataDog/datadog-api-client-python/pull/787).