DEV: Centralize user updates to a single MessageBus channel. (#17058)

Introduces an interface to publish user updates on the server side and
helps to reduce the growing number of subscriptions on the client side.

app/models/user.rb

@@ -657,16 +657,38 @@ class User < ActiveRecord::Base
     MessageBus.publish("/notification/#{id}", payload, user_ids: [id])
   end
 
+  PUBLISH_USER_STATUS_TYPE = "user_status"
+  PUBLISH_DO_NOT_STATUS_TYPE = "do_not_disturb"
+  PUBLISH_DRAFTS_TYPE = "drafts"
+
+  def self.publish_updates_channel(user_id)
+    "/user-updates/#{user_id}"
+  end
+
+  def self.publish_updates(user_id:, type:, payload:)
+    MessageBus.publish(
+      publish_updates_channel(user_id),
+      {
+        type: type,
+        payload: payload
+      },
+      user_ids: [user_id]
+    )
+  end
+
+  def publish_updates(type:, payload:)
+    self.class.publish_updates(user_id: id, type: type, payload: payload)
+  end
+
   def publish_do_not_disturb(ends_at: nil)
-    MessageBus.publish("/do-not-disturb/#{id}", { ends_at: ends_at&.httpdate }, user_ids: [id])
+    publish_updates(type: PUBLISH_DO_NOT_STATUS_TYPE, payload: { ends_at: ends_at&.httpdate })
   end
 
   def publish_user_status(status)
-    payload = status ?
-                { description: status.description, emoji: status.emoji } :
-                nil
-
-    MessageBus.publish("/user-status/#{id}", payload, user_ids: [id])
+    publish_updates(
+      type: PUBLISH_USER_STATUS_TYPE,
+      payload: status ? { description: status.description, emoji: status.emoji } : nil
+    )
   end
 
   def password=(password)

app/models/user_stat.rb

@@ -214,13 +214,13 @@ class UserStat < ActiveRecord::Base
         RETURNING draft_count, (SELECT 1 FROM drafts WHERE user_id = :user_id AND draft_key = :new_topic)
       SQL
 
-      MessageBus.publish(
-        "/user-drafts/#{user_id}",
-        {
+      User.publish_updates(
+        user_id: user_id,
+        type: User::PUBLISH_DRAFTS_TYPE,
+        payload: {
           draft_count: draft_count,
           has_topic_draft: !!has_topic_draft
-        },
-        user_ids: [user_id]
+        }
       )
     else
       DB.exec <<~SQL