Add initial workspace assignment capabilities to Rest API

Problem: 

Need to be able to fully automate onboarding existing AVD resources to Nerdio Manager. Currently, there does not appear to be an endpoint in the Nerdio Rest API which can be used to assign a workspace that does not already have at least 1 assignment. When trying to update an assignment with a workspace that does not already have an assignment via the "/api/v1/users-and-roles/assignment/{objectId}" endpoint, I receive the following error: "Error: The following workspaces cannot be assigned: {workspace_resource_id}". This is requiring us to have a manual break in resource registration in which a user must go into the Nerdio Manager portal and click "Assign".

Description:

Feature request for adding a Rest API endpoint for initial workspace assignments.