Introduce 'optional' validator to epp controllers

app/controllers/epp/keyrelays_controller.rb

@@ -21,18 +21,9 @@ class Epp::KeyrelaysController < EppController
       'authInfo', 'authInfo > pw'
     )
 
+    optional 'expiry > relative', duration_iso8601: true
+    optional 'expiry > absolute', date_time_iso8601: true
     exactly_one_of 'expiry > relative', 'expiry > absolute'
-
-    begin
-      abs_datetime = params[:parsed_frame].css('absolute').text
-      abs_datetime = DateTime.parse(abs_datetime) if abs_datetime.present?
-    rescue => _e
-      epp_errors << {
-        code: '2005',
-        msg: I18n.t('unknown_expiry_absolute_pattern'),
-        value: { obj: 'expiry_absolute', val: abs_datetime }
-      }
-    end
   end
   # rubocop: enable Metrics/PerceivedComplexity
   # rubocop: enable Metrics/CyclomaticComplexity

app/controllers/epp_controller.rb

@@ -92,6 +92,19 @@ class EppController < ApplicationController
     }
   end
 
+  def optional(selector, *validations)
+    full_selector = [@prefix, selector].join(' ')
+    el = params[:parsed_frame].css(full_selector).first
+    return unless el && el.text.present?
+    value = el.text
+
+    validations.each do |x|
+      validator = "#{x.first[0]}_validator".camelize.constantize
+      err = validator.validate_epp(selector.split(' ').last, value)
+      epp_errors << err if err
+    end
+  end
+
   def xml_attrs_present?(ph, attributes) # TODO: THIS IS DEPRECATED AND WILL BE REMOVED IN FUTURE
     attributes.each do |x|
       epp_errors << {