Migrate Azure Communication CallingServer to Call Automation

This is a migration skill for Azure Communication Services' deprecated CallingServer Java SDK, which has been renamed to Call Automation. It maps the concrete changes needed: swapping the Maven dependency from azure-communication-callingserver to azure-communication-callautomation (1.6.0), and renaming classes - CallingServerClient to CallAutomationClient, CallingServerClientBuilder to CallAutomationClientBuilder - while ServerCall is removed entirely in favor of CallConnection, which itself keeps its name unchanged. Client construction moves directly across:

// OLD WAY (deprecated)
import com.azure.communication.callingserver.CallingServerClient;
import com.azure.communication.callingserver.CallingServerClientBuilder;

CallingServerClient client = new CallingServerClientBuilder()
    .connectionString("<connection-string>")
    .buildClient();

// NEW WAY
import com.azure.communication.callautomation.CallAutomationClient;
import com.azure.communication.callautomation.CallAutomationClientBuilder;

CallAutomationClient client = new CallAutomationClientBuilder()
    .connectionString("<connection-string>")
    .buildClient();

Recording calls (startRecording/pauseRecording/resumeRecording/stopRecording) is shown in its old, deprecated form, with an explicit pointer to the azure-communication-callautomation skill for the current equivalent rather than duplicating it here.

Use this skill only when maintaining existing legacy code still on azure-communication-callingserver, or when actively migrating that legacy code to Call Automation. Do not use this SDK for any new development - the skill explicitly redirects new projects to the azure-communication-callautomation-java skill for outbound and inbound calling, recording, DTMF recognition, text-to-speech and speech-to-text, participant management, and call transfer, none of which this legacy skill covers in its current form.

Input is a codebase still depending on the deprecated azure-communication-callingserver artifact; output is the equivalent Maven dependency and import/class-name changes needed to move to azure-communication-callautomation, following the old-to-new mapping table for the classes that changed.

Java developers maintaining legacy Azure Communication Services code still on the CallingServer SDK who need to migrate it to Call Automation, not developers starting new calling-integration work.