Add the attribute for a cover image url for Book.

lib/decentralised_book_index/metadata.ex

@@ -39,6 +39,7 @@ defmodule DecentralisedBookIndex.Metadata do
       define :get_book_alternative_editions, args: [:book], action: :get_alternative_editions
       define :get_author_books, args: [:author], action: :get_author_books
       define :update_book, action: :update
+      define :assign_book_cover_image, args: [:cover_image_url], action: :assign_cover_image
       define :destroy_book, action: :destroy
     end
 

lib/decentralised_book_index/metadata/book.ex

@@ -100,6 +100,10 @@ defmodule DecentralisedBookIndex.Metadata.Book do
         |> Ash.Query.filter(expr(exists(author_roles, author_id in ^author_ids)))
       end
     end
+
+    update :assign_cover_image do
+      accept [:cover_image_url]
+    end
   end
 
   attributes do
@@ -135,6 +139,11 @@ defmodule DecentralisedBookIndex.Metadata.Book do
       public? true
     end
 
+    attribute :cover_image_url, :string do
+      allow_nil? true
+      public? true
+    end
+
     timestamps()
   end