Announcing the deprecation of the WIT and Test Client OM

Announces the deprecation of the Work Item Tracking (WIT) and Test SOAP APIs, which were part of the Microsoft.TeamFoundationServer.ExtendedClient. All work item and test methods in this client are marked as obsolete starting in Visual Studio 2019 and Azure DevOps Server 2019. The post recommends migrating to the REST APIs for new integrations and provides a deprecation matrix for SOAP and REST APIs across different Azure DevOps Server and Service versions. It also clarifies that while current WIT Client OM functionality is supported, no new features will be added to it.