Support for a file domain

[brandtkeller]

Generic file domain for processing a given target could open potential integrations with a variety of tools and reporting.

Notably CVE scanning tools such as Grype & Trivy provide json reporting output formats that Lula could consume and map to applicable controls / other OSCAL artifacts (Such as POAM). In-toto attestations are another example

Additional Context

Optimally this will be an area that allows for experimentation and testing prior to promoting optimizations of distinct scenarios into new domains.

Scope here should be a single file type (json) - but should support adding additional file type support.

Issue Deliverables

• Creation of a files domain
• Ability to specify a file path (local or remote) in a validation
• Ability to process a json file (otherwise error)
• Ability for each provider to accurately evaluate the data
  • OPA
  • Kyverno
• Docs
• Tests

Stretch Goal

• Add support for yaml files (otherwise create an issue for yaml support)