Dashboard step2: CF sso support

[gberche-orange]

As a service author, I need dashboard returned by nested brokers to be returned to end users.

I would like COAB to ensure that authN and authZ gets enforced, leveraging https://docs.cloudfoundry.org/services/dashboard-sso.html and service instance CC API permission, and leveraging the X-Api-Info-Location header to identify UAA location (while remaining compatible with #158) :

X-Api-Info-Location header containing the /v2/info url for that instance. The /v2/info endpoint will return further information, including the location of that Cloud Foundry instance’s UAA.

The nested broker would not add any additional authN and authZ, beyond only accepting traffic from the COAB service broker with alternative mechanisms such as:

• source IP address filtering (relies on Package COAB broker as a docker container #50 to have non volatile IP per broker)
• basic auth

Design:

• The X-Api-Info-Location header gets saved into coab-vars.yml at service instance creation.
• The dashboard URL returned contains the service instance guid such as /dashboard/guid
• A (dynamic?) spring oauth security configuration is performed so that the /dashboard/guid endpoint redirects to the UAA endpoint provided in the associated coab-vars.yml into the X-Api-Info-Location entry
• The endpoint controller's looks up the CF API endpoint into the associated coab-vars.yml into the X-Api-Info-Location entry, to invoke the /v2/service_instances/:guid/permissions endpoint

[gberche-orange]

lowering priority given that osb-cmdb should be given the responsibility