Update enforcer implementation for internal keys

[sgayangi]

• The APIM allows internal keys to be used to test out the API prior to publishing the API.
• On the APK side, this execution fails since the enforcer implementation checks subscription validation and scope validation, both of which fail, causing a request invoked with an internal key to fail.
• The enforcer implementation must be updated to

1. Remove subscription validation from JWT Authenticator
2. Skip scope validation for internal keys