Ingest ExternalReviews from K+

Adds a new entity ExternalChapterMetadata, which would allow us to
extend chapters to Recommendations, Ratings, etc in the future

API/DTOs/ChapterDetailPlusDto.cs

@@ -0,0 +1,14 @@
+#nullable enable
+using System.Collections.Generic;
+using API.DTOs.SeriesDetail;
+
+namespace API.DTOs;
+
+public class ChapterDetailPlusDto
+{
+    public float Rating { get; set; }
+    public bool HasBeenRated { get; set; }
+
+    public List<UserReviewDto> Reviews { get; set; }
+    public List<RatingDto>? Ratings { get; set; }
+}