[Feature]: Implement ViewpointUsageExtensions

[samatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the SysML2.NET
• I have searched open and closed issues to ensure it has not already been reported

Description

The ViewpointUsageExtensions class in SysML2.NET/Extend/ViewpointUsageExtensions.cs contains 2 extension method(s) that compute derived properties for the IViewpointUsage interface. These methods currently throw NotSupportedException and need to be implemented.

Checklist

• IViewpointDefinition ComputeViewpointDefinition(this IViewpointUsage)
• List<IPartUsage> ComputeViewpointStakeholder(this IViewpointUsage)

System Configuration

• SysML2.NET version: 0.19.0
• Source file: SysML2.NET/Extend/ViewpointUsageExtensions.cs