Add experimental server-side notification grouping (#29889)

db/migrate/20240513095755_add_group_key_to_notifications.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddGroupKeyToNotifications < ActiveRecord::Migration[7.1]
+  def change
+    add_column :notifications, :group_key, :string
+  end
+end

db/migrate/20240513123807_add_index_notifications_on_account_id_and_group_key.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddIndexNotificationsOnAccountIdAndGroupKey < ActiveRecord::Migration[7.1]
+  disable_ddl_transaction!
+
+  def change
+    add_index :notifications, [:account_id, :group_key], algorithm: :concurrently, where: 'group_key IS NOT NULL'
+  end
+end

db/schema.rb

@@ -724,6 +724,8 @@ ActiveRecord::Schema[7.1].define(version: 2024_05_22_041528) do
     t.bigint "from_account_id", null: false
     t.string "type"
     t.boolean "filtered", default: false, null: false
+    t.string "group_key"
+    t.index ["account_id", "group_key"], name: "index_notifications_on_account_id_and_group_key", where: "(group_key IS NOT NULL)"
     t.index ["account_id", "id", "type"], name: "index_notifications_on_account_id_and_id_and_type", order: { id: :desc }
     t.index ["account_id", "id", "type"], name: "index_notifications_on_filtered", order: { id: :desc }, where: "(filtered = false)"
     t.index ["activity_id", "activity_type"], name: "index_notifications_on_activity_id_and_activity_type"