Update AuthorRole to set author_id.

test/decentralised_book_index/metadata/author_roles_test.exs

@@ -0,0 +1,27 @@
+defmodule DecentralisedBookIndex.Metadata.AuthorRolesTest do
+  use DecentralisedBookIndex.DataCase, async: true
+
+  alias DecentralisedBookIndex.Metadata
+
+  describe "create action" do
+    test "an author's role must belongs to an author" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+
+      assert {:ok, author_role} = Metadata.create_author_role(author.id, 1, "role")
+
+      {:ok, author_role} =
+        author_role
+        |> Ash.load(:author)
+
+      assert author.id == author_role.author_id
+    end
+
+    test "an author's role can be blank" do
+      {:ok, author} = Metadata.create_author("Author", "An description")
+
+      {:ok, author_role} = Metadata.create_author_role(author.id, 1, "")
+
+      refute author_role.role
+    end
+  end
+end