[balancewebhooks] Code generation: update services and models

[AdyenAutomationBot]

This PR contains the automated changes for the balancewebhooks service.

The commit history of this PR reflects the adyen-openapi commits that have been applied.

[gemini-code-assist]

Code Review

This pull request removes several unused imports from the MessageHeaderTest class. A review comment suggests that instead of removing the assertNotNull import, it should be used to verify that the MessageHeader is correctly deserialized, which would enhance the test's robustness and provide clearer error messages.

[gemini-code-assist]

While this import is unused in the current code, consider re-adding it and using assertNotNull to verify that the deserializedMessageHeader object is not null after deserialization. This improves test clarity and provides a more specific error message if terminalApiGson.fromJson were to return null, which can aid in faster debugging.

For example, you could add the following after line 20:

assertNotNull(deserializedMessageHeader);