Add support for Core Authorization's User Roles and Permissions

[jakbutler]

Changes

• Added a new RolesEntity for providing access to the Role management API endpoints.
• Added supporting Role, Permission, RolesPage, and PermissionPage value objects, with respective deserializers.
• Added a RolesFilter for use in the get_roles call.
• Added a simple PageFilter for specifying filter objects that only contain pagination options, e.g. per_page and include_totals.
• Updated UserEntity to include User Permission and User Role endpoints.

References

Feature Request #192

Testing

• This change adds test coverage
• This change has been tested on the latest version of the platform/language

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors

[lbalmaceda]

@jakbutler thanks for taking care of this. I've added a review task to the backlog and I hope I can start with it the next week.

[jakbutler]

Apologies, I'd forgotten to also update the README.md to mention the Roles entity; that's been added now.

[martijnblankestijn]

Terrific work @jakbutler ! I was just researching how we could use the Roles API and found out it was missing. A very nice surprise to see this PR. I can't wait until a new release is being made with this feature added. I

[lbalmaceda]

Thanks for the PR! 🎉
I've left some comments. Some of them are repetitive, e.g. wrong formatting of java docs, methods to request all items vs paginated, etc. Know I've skipped reviewing tests and json files for now. This is a first pass. You'll probably end up deleting 1/4 of the diff introduced. I'll hold to that for completing the review 👍

[lbalmaceda]

Thanks!