Add OSCAL support

[alfinkel]

Overview

OSCAL will define a specific format for Assessment Results. We should add support to harvest report that can format results to meet that OSCAL format.

Requirements

• Provide the ability to format report content to meet the OSCAL Assessment Results format.

Approach

• Create a custom JSON encoder (??)
• Dependent upon OSCAL v2 implementation layer

Security and Privacy

N/A

Test Plan

TBD