Fix constraints and constraint test files per issue #773

[Rene2mt]

Committer Notes

This PR makes constraint, baseline, and example content (a.k.a. "template") updates to resolve issue #773

Specifically, it makes the following changes:

• For FedRAMP extension properties, changes namespace from "https://fedramp.gov/ns/oscal" to "http://fedramp.gov/ns/oscal"
• For the SSP identifier-type, changes the value from "https://fedramp.gov/ns/oscal" to "http://fedramp.gov/ns/oscal"
• For POA&M facets, changes the system flag from "https://fedramp.gov" to "http://fedramp.gov/ns/oscal"

All Submissions:

• Have you selected the correct base branch per Contributing guidance?
• Have you set "Allow edits and access to secrets by maintainers"?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you squashed any non-relevant commits and commit messages? [instructions]
• Have you added an explanation of what your changes do and why you'd like us to include them?
• If applicable, have all FedRAMP Documents Related to OSCAL Adoption affected by the changes in this issue have been updated.?
• If applicable, does this PR reference the issue it addresses and explain how it addresses the issue?

By submitting a pull request, you are agreeing to provide this contribution under the CC0 1.0 Universal public domain dedication.

[aj-stein-gsa]

@Rene2mt, I assume we are staging this PR for discussion on Wednesday, if I get your message and our previous conversations?

Either way, thanks for putting this work together. This will be useful to drive discussion.