fix: adds endpoint to support get-binding response for OSB v2.16

[TheSp1der]

The Open Service Broker API defines an endpoint object in the GET Binding Response that is not defined in the brokerapi response. This pull request adds an endpoint struct and updates the GetBindingReponse and GetBindingSpec to properly support the endpoints object.

[cf-gitbot]

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

https://www.pivotaltracker.com/story/show/187886817

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

[TheSp1der]

ready to review

[TheSp1der]

Ready for review. Thanks for putting up with my multiple commits to get this to pass checks!

[zucchinidev]

Thanks for raising the PR, we will study and analyse it and we'll come back to you soon.

[FelisiaM]

Thank you for your contribution @TheSp1der

The changes have now been released in v11.0.4