add private_map_quota field

db/migrate/20200120090245_add_private_map_quota.rb

@@ -0,0 +1,12 @@
+require 'carto/db/migration_helper'
+
+include Carto::Db::MigrationHelper
+
+migration(
+  Proc.new do
+    add_column :users, :private_map_quota, Integer, null: true
+  end,
+  Proc.new do
+    drop_column :users, :private_map_quota
+  end
+)