func (r *Href) ActionPath(rName, aName string) (*metadata.ActionPath, error) {
	res, ok := GenMetadata[rName]
	if !ok {
		return nil, fmt.Errorf("No resource with name '%s'", rName)
	}
	var action *metadata.Action
	for _, a := range res.Actions {
		if a.Name == aName {
			action = a
			break
		}
	}
	if action == nil {
		return nil, fmt.Errorf("No action with name '%s' on %s", aName, rName)
	}
	vars, err := res.ExtractVariables(string(*r))
	if err != nil {
		return nil, err
	}
	return action.URL(vars)
}
func (r *Href) ActionPath(rName, aName string) (*metadata.ActionPath, error) {
	res, ok := GenMetadata[rName]
	if !ok {
		return nil, fmt.Errorf("No resource with name '%s'", rName)
	}
	var action *metadata.Action
	for _, a := range res.Actions {
		if a.Name == aName {
			action = a
			break
		}
	}
	if action == nil {
		return nil, fmt.Errorf("No action with name '%s' on %s", aName, rName)
	}
	vars, err := res.ExtractVariables(string(*r))
	if err != nil {
		return nil, err
	}
	return action.URL(vars)
}
// ActionPath computes the path to the given resource action. For example given the href
// "/api/servers/123" calling ActionPath with resource "servers" and action "clone" returns the path
// "/api/servers/123/clone" and verb POST.
// The algorithm consists of extracting the variables from the href by looking up a matching
// pattern from the resource metadata. The variables are then substituted in the action path.
// If there are more than one pattern that match the href then the algorithm picks the one that can
// substitute the most variables.