FFI support for partial evaluation (for discussion)

[ygrignon-sfdc]

Description of changes

Adding support for partial evaluation for FFIs via the new json_is_authorized_partial function

Issue #, if available

#570

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A backwards-compatible change requiring a minor version bump to cedar-policy (e.g., addition of a new API).

I confirm that this PR (choose one, and delete the other options):

• Updates the "Unreleased" section of the CHANGELOG with a description of my change (required for major/minor version bumps).

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar Dafny model or DRT infrastructure.

Disclaimer

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[john-h-kastner-aws]

Hi @ygrignon-sfdc, thanks for the contribution! We'd all be excited to see partial evaluation added to the json interface (and presumably language bindings later on). We'll take a closer look and get back to you with any comments on the design/code.

[andrewmwells-amazon]

Looks good overall.

[john-h-kastner-aws]

Looks good to me.

I'll start the CI run (but most of the Build Downstream Dependencies targets are currently expected to fail due an issue in the scripts)

[andrewmwells-amazon]

Looking into the build failures. For one, you can run cargo fmt to fix. Alternatively, if you're happy with the current state, I can take over the PR to get CI passing.

[andrewmwells-amazon]

The other failures should hopefully be fixed by rebasing to pick up #574

[ygrignon-sfdc]

@andrewmwells-amazon I rebased my fork and addressed the fmt issues.
@john-h-kastner-aws got rid of the unwrap() you pointed to

[john-h-kastner-aws]

Looks good to me. Maybe @aaronjeline wants to look at this also