add mutations to questions and reviews

app/graphql/mutations/destroy_question.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module Mutations
+  class DestroyQuestion < BaseMutation
+    field :deleted_question_id, ID, null: true
+
+    argument :question_id, ID, required: true
+
+    def resolve(question_id:)
+      question = Question.find_by(id: question_id)
+      reviewer = question.reviewer
+
+      raise Pundit::NotAuthorizedError unless QuestionPolicy.new(context[:current_user], question).destroy?
+
+      return { errors: question.errors.full_messages } unless question.destroy!
+
+      ReviewerMailer.with(question_id: question_id, recipient: reviewer)
+        .question_deleted_notification
+        .deliver if reviewer
+
+      { deleted_question_id: question_id, errors: [] }
+    rescue Pundit::NotAuthorizedError => e
+      { errors: [e.message] }
+    end
+  end
+end