Changed design language. Added editions, better support for authors. Base for file handling

PageManager.Api/PageManager.Api.Tests/Helpers/BookFactory.cs

@@ -34,6 +34,7 @@ public static class BookFactory
             HardcoverId = hardcoverId,
             BookAuthors = [],
             SeriesEntries = [],
+            Editions = [],
         };
     }
 
@@ -53,6 +54,13 @@ public static class BookFactory
         return book;
     }
 
+    public static Book WithEditions(this Book book, params (string? Isbn, string? Publisher, string? CoverUrl)[] editions)
+    {
+        foreach (var (isbn, publisher, coverUrl) in editions)
+            book.Editions.Add(new Edition { BookId = book.Id, Isbn = isbn, Publisher = publisher, CoverUrl = coverUrl });
+        return book;
+    }
+
     public static Book WithSeries(this Book book, int seriesId = 1, string seriesName = "Test Series", double position = 1.0, string? arc = null)
     {
         var series = new Series { Id = seriesId, Name = seriesName };