Extract EE-specific lines from Gitlab::Email::Handler

lib/gitlab/email/handler.rb

@@ -6,15 +6,21 @@ require 'gitlab/email/handler/unsubscribe_handler'
 module Gitlab
   module Email
     module Handler
-      HANDLERS = [
-        UnsubscribeHandler,
-        CreateNoteHandler,
-        CreateMergeRequestHandler,
-        CreateIssueHandler
-      ].freeze
+      def self.handlers
+        @handlers ||= load_handlers
+      end
+
+      def self.load_handlers
+        [
+          UnsubscribeHandler,
+          CreateNoteHandler,
+          CreateMergeRequestHandler,
+          CreateIssueHandler
+        ]
+      end
 
       def self.for(mail, mail_key)
-        HANDLERS.find do |klass|
+        handlers.find do |klass|
           handler = klass.new(mail, mail_key)
           break handler if handler.can_handle?
         end

spec/lib/gitlab/email/handler_spec.rb

@@ -40,7 +40,7 @@ describe Gitlab::Email::Handler do
   end
 
   def ce_handlers
-    @ce_handlers ||= Gitlab::Email::Handler::HANDLERS.reject do |handler|
+    @ce_handlers ||= Gitlab::Email::Handler.handlers.reject do |handler|
       handler.name.start_with?('Gitlab::Email::Handler::EE::')
     end
   end