Addition of userPerspective to application schema

[clubycoder]

The physical perspective of the user vs the app is needed to properly group or exclude events in session as the majority of the time you will not want to include background or detached events in an active user session.

What are the schemas that are affected by the issue

https://github.com/adobe/xdm/blob/master/schemas/context/application.schema.json

What are examples of products that are impacted by the issue

Analytics and any other use-case that needs to understand groupings of events within a session.