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/Helpers/Builders/AppUserChapterRatingBuilder.cs

@@ -0,0 +1,40 @@
+#nullable enable
+using System;
+using API.Entities;
+
+namespace API.Helpers.Builders;
+
+public class ChapterRatingBuilder : IEntityBuilder<AppUserChapterRating>
+{
+    private readonly AppUserChapterRating _rating;
+    public AppUserChapterRating Build() => _rating;
+
+    public ChapterRatingBuilder(AppUserChapterRating? rating = null)
+    {
+        _rating = rating ?? new AppUserChapterRating();
+    }
+
+    public ChapterRatingBuilder WithSeriesId(int seriesId)
+    {
+        _rating.SeriesId = seriesId;
+        return this;
+    }
+
+    public ChapterRatingBuilder WithChapterId(int chapterId)
+    {
+        _rating.ChapterId = chapterId;
+        return this;
+    }
+
+    public ChapterRatingBuilder WithRating(int rating)
+    {
+        _rating.Rating = Math.Clamp(rating, 0, 5);
+        return this;
+    }
+
+    public ChapterRatingBuilder WithBody(string body)
+    {
+        _rating.Review = body;
+        return this;
+    }
+}