Code Review

This pull request introduces several new services to the Network Security API C++ client library, including Address Group, DNS Threat Detector, Firewall Activation, and Intercept. It generates the corresponding client, connection, stub, and decorator classes, and updates the documentation and configuration files. The review feedback highlights critical compilation errors in address_group_client.cc where iterators are incorrectly assigned to a RepeatedPtrField, and a formatting issue in CHANGELOG.md with an empty markdown link placeholder.