In `outputConfigs` object, allow parent properties to be specified and allow empty

[nikitawootten-nist]

User Story:

As a user of the tool, I would like to be able to produce excel reports of objects whose parents do not contain the same properties (e.g. comparing groups at the root of a catalog).

Currently if identifiers are specified in an outputConfigs item, the records are required to have these properties, and their parents must also contain them. This behavior limits the application of excel outputs to cases like an OSCAL catalog, which shares a title and id with its parent, group.

Goals:

• Add parentIdentifiers option (if omitted, default to no parent identifiers?)
• Allow identifiers and parentIdentifiers to have missing records (e.g. an OSCAL part optionally has an id)

Dependencies:

N/A

Acceptance Criteria

• [ ] readme documentation affected by the changes in this issue have been updated.
• [ ] A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• [ ] The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.