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.Infrastructure/Migrations/TvContextModelSnapshot.cs

@@ -794,6 +794,9 @@ namespace ErsatzTV.Infrastructure.Migrations
                         .ValueGeneratedOnAdd()
                         .HasColumnType("INTEGER");
 
+                    b.Property<string>("ContentRating")
+                        .HasColumnType("TEXT");
+
                     b.Property<DateTime>("DateAdded")
                         .HasColumnType("TEXT");
 
@@ -1170,6 +1173,9 @@ namespace ErsatzTV.Infrastructure.Migrations
                         .ValueGeneratedOnAdd()
                         .HasColumnType("INTEGER");
 
+                    b.Property<string>("ContentRating")
+                        .HasColumnType("TEXT");
+
                     b.Property<DateTime>("DateAdded")
                         .HasColumnType("TEXT");