Add new 'subscriptions_token' column to the users' table

Giving any user a direct link to edit another user's account settings doesn't seem like a
great idea. Instead we'll generate a random secure hash string to help keep things
more secure. We'll store these hashes on each user so that we have a way to find
them during this public query. To do this we need to add a column to the user table.

db/migrate/20201218082830_add_subscriptions_token_to_users.rb

@@ -0,0 +1,5 @@
+class AddSubscriptionsTokenToUsers < ActiveRecord::Migration[5.2]
+  def change
+    add_column :users, :subscriptions_token, :string
+  end
+end

db/schema.rb

@@ -1625,6 +1625,7 @@ ActiveRecord::Schema.define(version: 2021_11_03_112944) do
     t.boolean "public_interests", default: false
     t.boolean "recommended_debates", default: true
     t.boolean "recommended_proposals", default: true
+    t.string "subscriptions_token"
     t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
     t.index ["date_of_birth"], name: "index_users_on_date_of_birth"
     t.index ["email"], name: "index_users_on_email", unique: true