users表添加一些迁移

db/migrate/20190730024112_add_index_to_user.rb

@@ -0,0 +1,7 @@
+class AddIndexToUser < ActiveRecord::Migration[5.2]
+  def change
+    # add_index :users, :login, unique: true
+    # add_index :users, :mail, unique: true
+    # add_index :users, :phone, unique: true
+  end
+end