Add admin notifications for new Mastodon versions (#26582)

db/migrate/20230822081029_create_software_updates.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class CreateSoftwareUpdates < ActiveRecord::Migration[7.0]
+  def change
+    create_table :software_updates do |t|
+      t.string :version, null: false
+      t.boolean :urgent, default: false, null: false
+      t.integer :type, default: 0, null: false
+      t.string :release_notes, default: '', null: false
+
+      t.timestamps
+    end
+
+    add_index :software_updates, :version, unique: true
+  end
+end