Create test cases for all token modes

As we started working on porting the OpenPAYGO library to other programming languages it became apparent that need a good way to confirm the interop between those.

Ideally, we create a (potentially very long) JSON files which covers all token cases and acts as a source of truth. All libraries (including this one) should be equipped with CI test suit that runs tests against the provided JSON file.

The issue names no files or existing tests. Start by reviewing the token modes and current test and CI setup, then define the JSON source of truth and determine how this Python library should run against it. Done means all token cases are represented and the suite checks interoperability in CI.

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