SessionsController#create uses new DSO.

`SessionController#create` and `DSO2::SessionCreateAction` do pretty
much what you'd expect. Note the disparity in result handling for the
`#new` and `#create` methods; that will have to be revisited soon.

RSpec: 916 examples, 0 failures, 88 pending
RuboCop: 231 files inspected, no offenses detected