bring in sinon extensions for chai

S-47060
Ensure that the hypermediaResponse for digest is called when a post is made
to /api/digest.

The hypermedia responses were extracted out to a hypermediaResponse
module to house responses coming out of the controllers.

This is accomplished by using proxyquire to stub out the hypermediaResponse
module with a sinon spy in the place of digest.

S-47060