Docker CLI Contribution

This contribution resolved a longstanding issue in the Docker CLI regarding advanced networking setups. Previously, users could not assign a specific MAC address to a container dynamically when connecting it to a custom network post-creation. I implemented the `--mac-address` flag in the `docker network connect` command by updating the Go CLI bindings and ensuring seamless compatibility with the underlying Docker Engine API. This feature allows defining custom hardware addresses directly, significantly enhancing networking flexibility for complex testing scenarios and legacy application requirements.