Add the action to get author's ids.

lib/decentralised_book_index/metadata.ex

@@ -38,6 +38,7 @@ defmodule DecentralisedBookIndex.Metadata do
 
       define :list_authors, action: :read
       define :get_author_by_id, args: [:id], action: :by_id
+      define :get_author_ids, args: [:author], action: :get_author_ids
       define :get_author_alternative_names, args: [:author], action: :get_alternative_names
       define :search_author, action: :search, args: [:name]
       define :update_author, action: :update

lib/decentralised_book_index/metadata/author.ex

@@ -82,6 +82,22 @@ defmodule DecentralisedBookIndex.Metadata.Author do
       end
     end
 
+    action :get_author_ids, :vector do
+      argument :author, :struct, allow_nil?: false
+
+      run fn input, _ ->
+        author = input.arguments.author
+
+        {:ok, ids} =
+          DecentralisedBookIndex.Metadata.Author
+          |> Ash.Query.filter(author_alias_registry_id == ^author.author_alias_registry_id)
+          |> Ash.Query.select([:id])
+          |> Ash.read()
+
+        {:ok, Enum.map(ids, & &1.id)}
+      end
+    end
+
     read :search do
       argument :name, :ci_string do
         constraints allow_empty?: true