Consider separating the Hawk implementation from the Web API plumbing

[leastprivilege]

(and make it public)

Would allow re-use of your implementation in other contexts.

[pcibraro]

Yes, good idea. I was thinking in this when I initially wrote the the first implementation. The Hawk implementation is just an small fragment in the handler, but it makes sense to have it as a separate class.

[pcibraro]

Done