feat: Add support for system scope

[rsmayda]

Description of changes:

• Treat system scopes as user scopes as describe:

System scopes have the format system/(:resourceType|).(read|write|)– which conveys the same access scope as the matching user format user/(:resourceType|).(read|write|) https://hl7.org/fhir/uv/bulkdata/authorization/index.html#scopes

• Add testing to support new functionality
• In situations with sub is not provided in the JWT for system requests; an exception will be thrown

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.