[Ansible-service-broker] Proposal: broker authentication

[jesus m. rodriguez]

Continuing the specs for the sprint, here is the broker authentication
spec.

https://github.com/openshift/ansible-service-broker/pull/260

I'm doing things a little different for this spec. We tried doing
things a few different ways, I'm hoping this might be the best of all
worlds.

* spec as a github issue
  * public making it accessible
  * difficult to comment on specific line
  * difficult to keep track of comments
  * no history of revisions

* google docs
  * not able to make public outside Red Hat
  * ability to comment on specific lines
  * lengthy discussions were hard to keep track of
  * no history of revisions

Here is the hope for the PR process:

  * public
  * easy to comment on specific lines
  * familiar process to other code reviews
  * becomes part of the repo, can reference later
  * lengthy discussions seem easier to deal with

Sincerely,
jesus