This adds parsing and validation for grant strings along with the ability to create canonical JSON and text strings from a grant.
It also adds an ACL implementation, allowing a collection of grant strings to then be checked against a resource/action tuple and indicate if it's allowed.
Note that only specific sets of provided data in grant strings is allowed. This vastly simplifies logic.
Test coverage is 100%.
A future update will consolidate and migrate types between this and IAM but I didn't want to mix that in with this.
Jeff Mitchell