Extract hex_to_base36 and base36_to_hex methods in Uuid type

replacing normalize_base36. This should make it easier to convert
UUIDs between hex and base36 formats, useful when debugging production
logs that contain hex UUIDs.

For example, if in a log you see:

    User Load (0.3ms) SELECT `users`.* FROM `users` WHERE
    `users`.`account_id` = x'019afab815897a4f920f3a24fab75400' AND
    `users`.`id` = x'019afab815a2790688c58c7f8326e700' LIMIT 1

and you want to find that account or that user in the console, you can
now do:

    id = ActiveRecord::Type::Uuid.hex_to_base36("019afab815897a4f920f3a24fab75400")
    => "03f6bilrvt3oghzhurll4pp8g"

lib/rails_ext/active_record_uuid_type.rb

@@ -4,32 +4,34 @@ module ActiveRecord
     class Uuid < Binary
       BASE36_LENGTH = 25 # 36^25 > 2^128
 
-      def self.generate
+      class << self
-        uuid = SecureRandom.uuid_v7
+        def generate
-        hex = uuid.delete("-")
+          uuid = SecureRandom.uuid_v7
-        normalize_base36(hex.to_i(16))
+          hex = uuid.delete("-")
-      end
+          hex_to_base36(hex)
+        end
 
-      def self.normalize_base36(integer)
+        def hex_to_base36(hex)
-        integer.to_s(36).rjust(BASE36_LENGTH, "0")
+          hex.to_i(16).to_s(36).rjust(BASE36_LENGTH, "0")
+        end
+
+        def base36_to_hex(base36)
+          base36.to_s.to_i(36).to_s(16).rjust(32, "0")
+        end
       end
 
       def serialize(value)
         return unless value
 
-        binary = hex(value).scan(/../).map(&:hex).pack("C*")
+        binary = Uuid.base36_to_hex(value).scan(/../).map(&:hex).pack("C*")
         super(binary)
       end
 
-      def hex(value)
-        value.to_s.to_i(36).to_s(16).rjust(32, "0")
-      end
-
       def deserialize(value)
         return unless value
 
         hex = value.to_s.unpack1("H*")
-        Uuid.normalize_base36(hex.to_i(16))
+        Uuid.hex_to_base36(hex)
       end
 
       def cast(value)

test/test_helper.rb

@@ -154,8 +154,7 @@ module FixturesTestHelper
 
       # Format as UUID string and convert to base36 (25 chars)
       uuid = "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x" % bytes
-      hex = uuid.delete("-")
+      ActiveRecord::Type::Uuid.hex_to_base36(uuid.delete("-"))
-      hex.to_i(16).to_s(36).rjust(25, "0")
     end
   end
 end