FEATURE: Multiple Draft Topics (#30790)

Allows users to save multiple topic and personal message drafts,
allowing more flexibility around content creation.

The "New Topic" button will now always start a fresh topic. Drafts can
be resumed from the drafts dropdown menu or using the "My Drafts" link
in the sidebar.

Since drafts require a unique `draft_key` and `user_id` combination, we
have updated the format of the draft key for both topics and personal
messages. They will now have a prefix like "new_topic_" or
"new_message_" with the timestamp of when the composer was first opened
appended.

spec/serializers/current_user_serializer_spec.rb

@@ -128,28 +128,6 @@ RSpec.describe CurrentUserSerializer do
     end
   end
 
-  describe "#has_topic_draft" do
-    it "is not included by default" do
-      payload = serializer.as_json
-      expect(payload).not_to have_key(:has_topic_draft)
-    end
-
-    it "returns true when user has a draft" do
-      Draft.set(user, Draft::NEW_TOPIC, 0, "test1")
-
-      payload = serializer.as_json
-      expect(payload[:has_topic_draft]).to eq(true)
-    end
-
-    it "clearing a draft removes has_topic_draft from payload" do
-      sequence = Draft.set(user, Draft::NEW_TOPIC, 0, "test1")
-      Draft.clear(user, Draft::NEW_TOPIC, sequence)
-
-      payload = serializer.as_json
-      expect(payload).not_to have_key(:has_topic_draft)
-    end
-  end
-
   describe "#can_ignore_users" do
     let(:guardian) { Guardian.new(user) }
     let(:payload) { serializer.as_json }