Walk the registry and add sphinx directives

def register_references(kb_app: kb,
                        sphinx_app: Sphinx,
                        sphinx_env: BuildEnvironment,
                        docnames: List[str]):
    """ Walk the registry and add sphinx directives """

    references: ReferencesContainer = sphinx_app.env.references

    for name, klass in kb_app.config.resources.items():
        # Name is the value in the decorator and directive, e.g.
        # @kb.resource('category') means name=category
        if getattr(klass, 'is_reference', False):
            references[name] = dict()