[PoC] Adds FxA OAuth support

### Proof of Concept 

ref https://bugzilla.mozilla.org/show_bug.cgi?id=1022064
There is an earlier config, not sure which one is preferred. Should I update both or just oauth?
``` 
tokBox: { 
doc: "TokBox service config", 
format: validateKeys(["apiKey", "apiSecret", "tokenDuration"]), 
default: "" }, 
```