Add `memorial` attribute to REST API (#23591)

app/serializers/rest/account_serializer.rb

@@ -16,6 +16,8 @@ class REST::AccountSerializer < ActiveModel::Serializer
   attribute :silenced, key: :limited, if: :silenced?
   attribute :noindex, if: :local?
 
+  attribute :memorial, if: :memorial?
+
   class AccountDecorator < SimpleDelegator
     def self.model_name
       Account.model_name
@@ -124,6 +126,10 @@ class REST::AccountSerializer < ActiveModel::Serializer
     object.silenced?
   end
 
+  def memorial
+    object.memorial?
+  end
+
   def roles
     if object.suspended? || object.user.nil?
       []
@@ -136,7 +142,7 @@ class REST::AccountSerializer < ActiveModel::Serializer
     object.user_prefers_noindex?
   end
 
-  delegate :suspended?, :silenced?, :local?, to: :object
+  delegate :suspended?, :silenced?, :local?, :memorial?, to: :object
 
   def moved_and_not_nested?
     object.moved?

spec/serializers/rest/account_serializer_spec.rb

@@ -34,4 +34,14 @@ describe REST::AccountSerializer do
       expect(subject['roles']).to eq []
     end
   end
+
+  context 'when the account is memorialized' do
+    before do
+      account.memorialize!
+    end
+
+    it 'marks it as such' do
+      expect(subject['memorial']).to be true
+    end
+  end
 end