ArcGIS Pro 2.7 API Reference Guide
IServerObjectExtension Interface
Members 

ArcGIS.Desktop.Core.Sharing Namespace : IServerObjectExtension Interface
This interface is used to implement support for external custom SOE, external custom soe addin need implemeant this interface.
Syntax
public interface IServerObjectExtension 
Public Interface IServerObjectExtension 
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

IServerObjectExtension Members
ArcGIS.Desktop.Core.Sharing Namespace