Cannot run the BGD using 'buildpacks'

[rudi-matricata]

In the manifest that is used for deployment (BGD) you can specify 'buildpacks'. Since 'buildpack' is deprecated it is better to specify it as:

---
    ...
    buildpacks:
      - buildpack_URL

• https://docs.cloudfoundry.org/devguide/deploy-apps/manifest-attributes.html#buildpack

When you execute the bgd command with this manifest you get the response:

'Could not push new version - Error reading manifest file:
buildpack must be a string or null value'

[holly-cummins]

I think this is probably a duplicate of #89 and #83. The underlying issue is that the cf cli plugin architecture doesn't support the new manifest fields. The workaround is to re-architect this plugin to use fewer of the cf APIs to remove the dependency on the legacy parts of the framework API.