Hi Michael,
What you've said about using the `client_credentials` grant to protect the client secret makes sense.
The problen I have is that the ValidationService in oxd seems to be treating the request to the token (RPT) endpoint as a PAT, and complains that the token does not have the `oxd` grant, which of course it wouldn't, because it's just the client credentials.
```
2019-02-14 19:35:04,795 TRACE [org.xdi.oxd.server.service.ValidationService] access_token: a933b772-6035-4a6f-8b75-f531a9706b01, introspection: IntrospectionResponse{active=true, scopes=[], scope=[], clientId='@!3932.OBFUSCATED-FOR-TICKET', username='null', tokenType='bearer', expiresAt=1550173108, issuedAt=1550172808, subject='', audience='@!3932.OBFUSCATED-FOR-TICKET', issuer='https://auth.azya.io', jti='null', acrValues='null'}, setupClientId: @!3932.OTHER-OBFUSCATED-FOR-TICKET
2019-02-14 19:35:04,795 ERROR [org.xdi.oxd.server.Processor]
ErrorResponseException{errorResponseCode=ErrorResponseCode{value='protection_access_token_insufficient_scope', description='protection_access_token does not have oxd scope. Make sure a) scope exists on AS b) setup_client is registered with 'oxd' scope c) get_client_token has 'oxd' scope in request'}}
at org.xdi.oxd.server.service.ValidationService.validate(ValidationService.java:139)
at org.xdi.oxd.server.service.ValidationService.validate(ValidationService.java:49)
```
Note that the introspected token `a933b772-6035-4a6f-8b75-f531a9706b01` was the client_credential token.
I don't see any way pass that Validation error other than using the "PAT" originally provided via the oxd-https-extension API's /get-client-token resource...