Revert "Unify ChapterRating with Rating"

This wasn't working out, there is still some duplicate code. But not
that much, and from the API, there is no different. Hooray!

API/Entities/AppUserChapterRating.cs

@@ -0,0 +1,30 @@
+namespace API.Entities;
+
+public class AppUserChapterRating
+{
+    public int Id { get; set; }
+    /// <summary>
+    /// A number between 0-5.0 that represents how good a series is.
+    /// </summary>
+    public float Rating { get; set; }
+    /// <summary>
+    /// If the rating has been explicitly set. Otherwise, the 0.0 rating should be ignored as it's not rated
+    /// </summary>
+    public bool HasBeenRated { get; set; }
+    /// <summary>
+    /// A short summary the user can write when giving their review.
+    /// </summary>
+    public string? Review { get; set; }
+    /// <summary>
+    /// An optional tagline for the review
+    /// </summary>
+    public int SeriesId { get; set; }
+    public Series Series { get; set; } = null!;
+
+    public int ChapterId { get; set; }
+    public Chapter Chapter { get; set; } = null!;
+
+    // Relationships
+    public int AppUserId { get; set; }
+    public AppUser AppUser { get; set; } = null!;
+}