Add NewtonsoftJson to Swagger

Add RetrieveChaptersJob.cs
Add UpdateFilesDownloadedJob.cs
Remove DownloadNewChaptersJob.cs and instead use DownloadAvailableChaptersJob.cs

API/Schema/Jobs/RetrieveChaptersJob.cs

@@ -0,0 +1,36 @@
+using System.ComponentModel.DataAnnotations;
+using API.Schema.MangaConnectors;
+using Newtonsoft.Json;
+
+namespace API.Schema.Jobs;
+
+public class RetrieveChaptersJob(ulong recurrenceMs, string mangaId, string? parentJobId = null, ICollection<string>? dependsOnJobsIds = null)
+    : Job(TokenGen.CreateToken(typeof(RetrieveChaptersJob)), JobType.RetrieveChaptersJob, recurrenceMs, parentJobId, dependsOnJobsIds)
+{
+    [MaxLength(64)]
+    public string MangaId { get; init; } = mangaId;
+    
+    [JsonIgnore]
+    public Manga? Manga { get; init; }
+    
+    protected override IEnumerable<Job> RunInternal(PgsqlContext context)
+    {
+        /*
+         * For some reason, directly using Manga from above instead of finding it again causes DBContext to consider
+         * Manga as a new entity and Postgres throws a Duplicate PK exception.
+         * m.MangaConnector does not have this issue (IDK why).
+         */ 
+        Manga m = context.Manga.Find(MangaId)!; 
+        MangaConnector connector = context.MangaConnectors.Find(m.MangaConnectorId)!;
+        // This gets all chapters that are not downloaded
+        Chapter[] allNewChapters = connector.GetNewChapters(m);
+        
+        // This filters out chapters that are not downloaded but already exist in the DB
+        string[] chapterIds = context.Chapters.Where(chapter => chapter.ParentMangaId == m.MangaId).Select(chapter => chapter.ChapterId).ToArray();
+        Chapter[] newChapters = allNewChapters.Where(chapter => !chapterIds.Contains(chapter.ChapterId)).ToArray();
+        context.Chapters.AddRangeAsync(newChapters).Wait();
+        context.SaveChangesAsync().Wait();
+
+        return [];
+    }
+}