CRD Schema Generator - Ignore Non-Exported Fields

[ryantse]

In certain CRD structs in Go, a developer may choose to not to have a field be part of the schema by using "-" as the JSON field name. Currently, the generator does not handle this case and improperly generates a JSON Schema that has this as a field name, this subsequently fails during JSON Schema to POJO generation as a field should not be called "-".

A concrete example of this use can be found in the RolloutSpec for Argo Rollouts: https://github.com/argoproj/argo-rollouts/blob/master/pkg/apis/rollouts/v1alpha1/types.go#L36-L37

The generator should be made aware of this functionality and not export these fields to the JSON Schema.