Adapt code to work with frozen strings

app/models/enterprise_group.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'open_food_network/locking'
 require 'open_food_network/permalink_generator'
 require 'spree/core/s3_support'
@@ -66,10 +68,10 @@ class EnterpriseGroup < ActiveRecord::Base
   def unset_undefined_address_fields
     return if address.blank?
 
-    address.phone.sub!(/^#{I18n.t(:undefined)}$/, '')
-    address.address1.sub!(/^#{I18n.t(:undefined)}$/, '')
-    address.city.sub!(/^#{I18n.t(:undefined)}$/, '')
-    address.zipcode.sub!(/^#{I18n.t(:undefined)}$/, '')
+    address.phone = address.phone.sub(/^#{I18n.t(:undefined)}$/, '')
+    address.address1 = address.address1.sub(/^#{I18n.t(:undefined)}$/, '')
+    address.city = address.city.sub(/^#{I18n.t(:undefined)}$/, '')
+    address.zipcode = address.zipcode.sub(/^#{I18n.t(:undefined)}$/, '')
   end
 
   def to_param

lib/open_food_network/locking.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module OpenFoodNetwork::Locking
   # http://rhnh.net/2010/06/30/acts-as-list-will-break-in-production
   def with_isolation_level_serializable

lib/open_food_network/permalink_generator.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Finds a unique permalink for a new or updated record.
 # It considers soft-deleted records which are ignored by Spree.
 # Spree's work:

spec/models/spree/product_spec.rb

@@ -1,4 +1,4 @@
-# frozen_string_literal: true
+# frozen_string_literal: false
 
 require 'spec_helper'
 require 'spree/core/product_duplicator'