Not able to use the Object struct on operator based project.

[spolti]

What happened:

Interface types are not well handled by the operator-sdk controller gen. In cases similar to:

// IObject interface that can converted into one of the three subtypes
type IObject interface {
	DeepCopyIObject() IObject
}

While trying to build the Operator a similar issue will happen:

/src/github.com/serverlessworkflow/sdk-go/model/Object.go:40:21: unsupported AST kind *ast.InterfaceType

Fixed by #139