feat: use -1 for not listed address for extensibility

app/models/form/lettings/questions/address_selection.rb

@@ -31,7 +31,7 @@ class Form::Lettings::Questions::AddressSelection < ::Form::Question
       "8" => { "value" => values[8] },
       "9" => { "value" => values[9] },
       "divider" => { "value" => true },
-      "10" => { "value" => "The address is not listed, I want to enter the address manually" },
+      "-1" => { "value" => "The address is not listed, I want to enter the address manually" },
     }.freeze
   end
 

app/models/log.rb

@@ -97,7 +97,7 @@ class Log < ApplicationRecord
         self.postcode_full = presenter.postcode
         self.county = nil
         process_postcode_changes!
-      elsif address_selection == 10
+      elsif address_selection == -1
         self.uprn_known = 0
         self.uprn_confirmed = nil
         self.uprn = nil