Bump rails to 5.2 and update rubocop

app/models/concerns/findable_with_token.rb

@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 #
 # Make a model findable only when a secure token is provided.
 #
 module FindableWithToken
   extend ActiveSupport::Concern
 
-  ID_TOKEN_RX = /\A(\d+)-(\w+)\z/
+  ID_TOKEN_RX = /\A(\d+)-(\w+)\z/.freeze
 
   included do
     has_secure_token
@@ -15,12 +17,14 @@ module FindableWithToken
 
     def self.find_by_id_token(id_token)
       raise ActiveRecord::RecordNotFound unless id_token =~ ID_TOKEN_RX
+
       id = Regexp.last_match(1)
       token = Regexp.last_match(2)
 
       record = find(id)
       raise ActiveRecord::RecordNotFound unless
         ActiveSupport::SecurityUtils.secure_compare(record.token, token)
+
       record
     end
   end