[FR] Support plan metadata field cost

[kanngiesser]

Is your feature request related to a problem? Please describe.
The Open Service Broker API Specification describes conventions for the opaque plan metadata field on the Service Plan Object which is returned from /v2/catalog requests.

The Cloud-Service-Broker supports most of the fields which are described in the specification: It is possible to define values for metdata.display_name and metadata.bullets by adding the respective fields to the service definition yml (see Brokerpak specification), but metadata.cost is missing. We require this information to make cost information available to our internal customers.

Describe the solution you'd like

It is possible to define cost information for the plan object (from yml service definition or environment variable GSB_SERVICE_SERVICE_NAME_PLAN):

plans:
  - name: standard
    id: dc939a71-d3d7-40d7-b9e7-9889d9270743
    display_name: standard
    description: standard plan
    free: false
    costs:
       - unit: Monthly
         amount: 
           EUR: 0.85
           USD: 1.00

Cost Metadata should is added to Brokerpak Specification

The Server returns cost information at the v2/catalog endpoint

Describe alternatives you've considered

Additional Context

Priority
Low

Priority Context

Platform
AWS

Applicable Services
all services and plans

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/187910594

The labels on this github issue will be updated when the story is started.

[ifindlay-cci]

@kanngiesser The team do not have the capacity to address this, however we are open to contributions. Would you like to submit a PR?