func NewITunesFeedExtension(extensions map[string][]Extension) *ITunesFeedExtension {
	feed := &ITunesFeedExtension{}
	feed.Author = parseTextExtension("author", extensions)
	feed.Block = parseTextExtension("block", extensions)
	feed.Explicit = parseTextExtension("explicit", extensions)
	feed.Keywords = parseTextExtension("keywords", extensions)
	feed.Subtitle = parseTextExtension("subtitle", extensions)
	feed.Summary = parseTextExtension("summary", extensions)
	feed.Image = parseImage(extensions)
	feed.Complete = parseTextExtension("complete", extensions)
	feed.NewFeedURL = parseTextExtension("new-feed-url", extensions)
	feed.Categories = parseCategories(extensions)
	feed.Owner = parseOwner(extensions)
	return feed
}
NewITunesFeedExtension creates an ITunesFeedExtension given an
extension map for the "itunes" key.
package ext
type ITunesFeedExtension struct {
	Author     string            `json:"author,omitempty"`
	Block      string            `json:"block,omitempty"`
	Categories []*ITunesCategory `json:"categories,omitempty"`
	Explicit   string            `json:"explicit,omitempty"`
	Keywords   string            `json:"keywords,omitempty"`
	Owner      *ITunesOwner      `json:"owner,omitempty"`
	Subtitle   string            `json:"subtitle,omitempty"`
	Summary    string            `json:"summary,omitempty"`
	Image      string            `json:"image,omitempty"`
	Complete   string            `json:"complete,omitempty"`
	NewFeedURL string            `json:"newFeedUrl,omitempty"`
}
type ITunesItemExtension struct {
	Author            string `json:"author,omitempty"`
	Block             string `json:"block,omitempty"`
	Duration          string `json:"duration,omitempty"`
	Explicit          string `json:"explicit,omitempty"`
	Keywords          string `json:"keywords,omitempty"`
	Subtitle          string `json:"subtitle,omitempty"`
	Summary           string `json:"summary,omitempty"`
	Image             string `json:"image,omitempty"`
	IsClosedCaptioned string `json:"isClosedCaptioned,omitempty"`
	Order             string `json:"order,omitempty"`
}
type ITunesCategory struct {
	Text        string          `json:"text,omitempty"`
	Subcategory *ITunesCategory `json:"subcategory,omitempty"`
}
type ITunesOwner struct {
	Email string `json:"email,omitempty"`
	Name  string `json:"name,omitempty"`
}