Implement GraphQL Edition type withdrawn_notice

Currently content items for non-withdrawn editions will include an empty
object for the `withdrawn_notice`. We opted to return `nil` instead,
which feels more conventional (for APIs in general) and is also the
[recommended way of doing things in GraphQL][1]. Implementing an empty
object in GraphQL requires some fairly [hacky code][2]. We'll need to
ensure that consumers can handle this field being `nil` before any move
to use the GraphQL endpoint in production

[1]: https://spec.graphql.org/draft/#sel-HAHZhCFBABPBT5pS
[2]: graphql/graphql-spec#568 (comment)

Co-authored-by: George <[email protected]>

Author: yndajas

app/graphql/types/edition_type.rb

@@ -2,6 +2,11 @@
 
 module Types
   class EditionType < Types::BaseObject
+    class WithdrawnNotice < Types::BaseObject
+      field :explanation, String
+      field :withdrawn_at, GraphQL::Types::ISO8601DateTime
+    end
+
     field :analytics_identifier, String
     field :base_path, String
     field :content_id, ID
@@ -20,7 +25,16 @@ class EditionType < Types::BaseObject
     field :schema_name, String
     field :title, String, null: false
     field :updated_at, GraphQL::Types::ISO8601DateTime
-    field :withdrawn_notice, String
+    field :withdrawn_notice, WithdrawnNotice
+
+    def withdrawn_notice
+      return nil unless object.unpublishing&.withdrawal?
+
+      Presenters::EditionPresenter
+        .new(object)
+        .present
+        .fetch(:withdrawn_notice)
+    end
 
     # Aliased by field methods for fields that are currently presented in the
     # content item, but come from Content Store, so we can't provide them here

spec/graphql/types/edition_type_spec.rb

@@ -0,0 +1,33 @@
+RSpec.describe "Types::EditionType" do
+  include GraphQL::Testing::Helpers.for(PublishingApiSchema)
+
+  describe "#withdrawn_notice" do
+    context "when the edition is withdrawn" do
+      it "returns a withdrawal notice" do
+        edition = create(:withdrawn_unpublished_edition, explanation: "for testing", unpublished_at: "2024-10-28 17:00:00.000000000 +0000")
+        expected = {
+          explanation: "for testing",
+          withdrawn_at: "2024-10-28T17:00:00Z",
+        }
+
+        expect(
+          run_graphql_field(
+            "Edition.withdrawnNotice",
+            edition,
+          ),
+        ).to eq(expected)
+      end
+    end
+
+    context "when the edition is not withdrawn" do
+      it "returns nil" do
+        expect(
+          run_graphql_field(
+            "Edition.withdrawnNotice",
+            create(:edition),
+          ),
+        ).to be_nil
+      end
+    end
+  end
+end

spec/integration/graphql_spec.rb

@@ -59,10 +59,7 @@
             "schemaName": @edition.schema_name,
             "title": @edition.title,
             "updatedAt": @edition.updated_at.iso8601,
-            "withdrawnNotice": {
-              "explanation": nil,
-              "withdrawnAt": nil,
-            },
+            "withdrawnNotice": nil,
           },
         },
       }
@@ -72,6 +69,48 @@
       expect(parsed_response).to eq(expected)
     end
 
+    context "when there is a withdrawn notice" do
+      before do
+        create(
+          :withdrawn_unpublished_edition,
+          base_path: "/my/withdrawn/edition",
+          explanation: "for integration testing",
+          unpublished_at: "2024-10-27 17:00:00.000000000 +0000",
+        )
+      end
+
+      it "populates the withdrawn notice" do
+        post "/graphql", params: {
+          query:
+            "{
+              edition(basePath: \"/my/withdrawn/edition\") {
+                ... on Edition {
+                  withdrawnNotice {
+                    explanation
+                    withdrawnAt
+                  }
+                }
+              }
+            }",
+        }
+
+        expected = {
+          "data": {
+            "edition": {
+              "withdrawnNotice": {
+                "explanation": "for integration testing",
+                "withdrawnAt": "2024-10-27T17:00:00Z",
+              },
+            },
+          },
+        }
+
+        parsed_response = JSON.parse(response.body).deep_symbolize_keys
+
+        expect(parsed_response).to eq(expected)
+      end
+    end
+
     it "does not expose non-generic edition fields" do
       post "/graphql", params: {
         query: