Fix invalid field name

Author: laurentpellegrino

CHANGELOG.md

@@ -9,9 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [4.3.0] - 2021-12-14
 ### Added
-- New `parse` method in IpregistryClient for parsing user-agent header values.
+- New `parse` method in _IpregistryClient_ for parsing user-agent header values.
 ### Deprecated
 - Deprecate `IpregistryConfigBuilder.withApiUrl` in favor of `IpregistryConfigBuilder.withBaseUrl`. 
+### Fixed
+- Replace invalid `operating_system` field in _UserAgent_ by `os`.
 
 ## [4.2.0] - 2021-10-26
 ### Added

src/model.ts

@@ -60,7 +60,7 @@ export interface UserAgent {
 
     engine: UserAgentEngine;
 
-    operating_system: UserAgentOperatingSystem;
+    os: UserAgentOperatingSystem;
 
 }