add user scaffold

db/migrate/20220227172543_create_users.rb

@@ -0,0 +1,9 @@
+class CreateUsers < ActiveRecord::Migration[7.0]
+  def change
+    create_table :users do |t|
+      t.string :username, null: false, limit: 14, index: true
+
+      t.timestamps
+    end
+  end
+end