Eliminate nil/empty distinction for new v1 field

[ironcladlou]

Ensure there is no internal or external distinction between nil and
empty BrokerTemplateInstanceSpec.BindingIDs to enable maximum
compatibility with stored serialized types (e.g. protobufs).

Part of #13419.

[ironcladlou]

[test]

[ironcladlou]

/cc @liggitt

[liggitt]

LGTM, would like second from @jim-minter as original author

[jim-minter]

@ironcladlou thanks for doing this. Please additionally remove line https://github.com/openshift/origin/blob/master/test/extended/templates/templateservicebroker_e2e.go#L145 (BindingIDs: []string{}, and you'll be all set.

[jim-minter]

also - is there any documentation / unit test that already exists or which can be put in place to prevent people like me making this mistake again?

[ironcladlou]

@jim-minter

@ironcladlou thanks for doing this. Please additionally remove line https://github.com/openshift/origin/blob/master/test/extended/templates/templateservicebroker_e2e.go#L145 (BindingIDs: []string{}, and you'll be all set.

Thanks!

also - is there any documentation / unit test that already exists or which can be put in place to prevent people like me making this mistake again?

@liggitt had a test in a related upstream PR which ensured that slice fields missing omitempty serialized nil/empty to []; it seems possible to make a conceptually similar test in origin which ensures that all non-whitelisted API slice fields contain omitempty to enforce going forward.

@liggitt, does such a unit test seem valuable here?

[ironcladlou]

Hit a test flake. Went ahead and squashed to try one more run before merging.

ref #14573

[openshift-bot]

Evaluated for origin test up to 6bd4c9d

[openshift-bot]

continuous-integration/openshift-jenkins/test SUCCESS (https://ci.openshift.redhat.com/jenkins/job/test_pull_request_origin/2165/) (Base Commit: 6d3e523)

[ironcladlou]

[merge]

[openshift-bot]

Evaluated for origin merge up to 6bd4c9d

[smarterclayton]

[severity:bug]

[openshift-bot]

continuous-integration/openshift-jenkins/merge SUCCESS (https://ci.openshift.redhat.com/jenkins/job/merge_pull_request_origin/1001/) (Base Commit: 2df56bd) (Extended Tests: bug) (Image: devenv-rhel7_6361)