add content rating (#218)

* add new columns

* store local content ratings

* display and search content ratings

* add content_rating to search docs

* sync content rating from jellyfin, emby, plex

* force sync content rating for all libraries

* code cleanup

ErsatzTV.Application/Movies/Mapper.cs

@@ -26,6 +26,8 @@ namespace ErsatzTV.Application.Movies
                 metadata.Genres.Map(g => g.Name).ToList(),
                 metadata.Tags.Map(t => t.Name).ToList(),
                 metadata.Studios.Map(s => s.Name).ToList(),
+                (metadata.ContentRating ?? string.Empty).Split("/").Map(s => s.Trim())
+                .Where(x => !string.IsNullOrWhiteSpace(x)).ToList(),
                 LanguagesForMovie(movie),
                 metadata.Actors.OrderBy(a => a.Order).ThenBy(a => a.Id)
                     .Map(a => MediaCards.Mapper.ProjectToViewModel(a, maybeJellyfin, maybeEmby))