Merge pull request 'Added GetBookByProductId()' (#100) from payments into master

Reviewed-on: #100

LiteCharms.Features.MidrandBooks/AuthorBooks/BooksService.cs

@@ -58,6 +58,30 @@ public sealed class BooksService(IDbContextFactory<MidrandBooksDbContext> contex
         }
     }
 
+    public async ValueTask<Result<AuthorBook>> GetBookByProductIdAsync(long productId, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            await using var context = await contextFactory.CreateDbContextAsync(cancellationToken);
+
+            var book = await context.Books
+                .AsNoTracking()
+                .Include(b => b.Author)
+                .Include(b => b.Product)
+                    .ThenInclude(b => b!.Prices)
+                .Include(b => b.Pages)
+                .FirstOrDefaultAsync(b => b.ProductId == productId, cancellationToken);
+
+            return book is null
+                ? Result.Fail<AuthorBook>(new Error($"Book with product ID {productId} not found"))
+                : Result.Ok(book.ToModel());
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail<AuthorBook>(new Error(ex.Message).CausedBy(ex));
+        }
+    }
+
     public async ValueTask<Result<AuthorBook>> GetBookAsync(long bookId, CancellationToken cancellationToken = default)
     {
         try