Was testing code from this pull request in an attempt to get Restlet with OAuth 2.0 working in OSGi environment.
MemoryClient#isResponseTypeAllowed seems an endless recursion which resulted in StackOverflowException.
I temporarily fixed this in my environment by exclusively returning true.

But noticing the method MemoryClient#isFlowSupported takes an Object parameter instead of GrantType, then maybe isFlowSupported(responseType) should be used?