retitle test

S-47060
the response from creating a digest should contain a rel to go create
an inbox

S-47060
the method to access the inbox-form is via a an http GET
A second style for accessing the inbox-form link from the response of
creating an inbox.

It's debateable which style is better. I thought about this style because
doing it this way removes you from having to know what position in the
_links array the inbox-form link is. knowing the position seemed to me too
tightly couple the test to the implementation.

I've left both in the tests to have a chat with folks about their
opinions.
there should be a reference to the inbox form endpoint.