Apply the Cedar schema terminology

[shaobo-he-aws]

Description of changes

Issue #, if available

842

Checklist for requesting a review

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

• [x] A breaking change requiring a major version bump to cedar-policy (e.g., changes to the signature of an existing API).

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

• [x] 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):

• [x] Requires updates, and I have made / will make these updates myself. (Please include in your description a timeline or link to the relevant PR in cedar-spec, and how you have tested that your updates are correct.)

[shaobo-he-aws]

All APIs and comments should be updated. The remaining work is to rename tests, which I will do once a preliminary review is done.

[shaobo-he-aws]

I like the proposed renaming.

Will this extend to renaming the policy format?

Good idea. Craig just did it.

[shaobo-he-aws]

Overall, the changes look good. The new names are more consistent.

But I'd prefer more symmetry between the public (aka defined in api.rs) PolicySet and Schema interfaces. For PolicySet we provide:

• a FromStr impl (which parses the Cedar syntax)
• from_json_str
• from_json_value
• from_json_file
• to_json

I think we should provide the same sort of interface for Schema and SchemaFragment. So:

• the FromStr impl should parse the Cedar syntax, and we should have a separate from_json_str to parse the JSON syntax
• from_file should be renamed from_json_file
• from_file_cedar should be renamed to from_file
• maybe rename as_cedar to to_cedar

How about using the file suffix (cedarschema vs json) to name these APIs? For instance,

• Schema::from_str_cedar to Schema::from_cedarschema_str
• Schema::from_file_cedar to Schema::from_cedarschema_file
• SchemaFragment::as_cedar to SchemaFragment::to_cedarschema