add an incoming email handler for service desk

lib/gitlab/email/handler.rb

@@ -2,10 +2,13 @@ require 'gitlab/email/handler/create_note_handler'
 require 'gitlab/email/handler/create_issue_handler'
 require 'gitlab/email/handler/unsubscribe_handler'
 
+require 'gitlab/email/handler/ee/service_desk_handler'
+
 module Gitlab
   module Email
     module Handler
       HANDLERS = [
+        EE::ServiceDeskHandler,
         UnsubscribeHandler,
         CreateNoteHandler,
         CreateIssueHandler,

lib/gitlab/email/handler/ee/service_desk_handler.rb

+module Gitlab
+  module Email
+    module Handler
+      module EE
+        class ServiceDeskHandler < BaseHandler
+          include ReplyProcessing
+
+          def can_handle?
+            Gitlab::EE::ServiceDesk.enabled? && service_desk_key.present?
+          end
+
+          def execute
+            raise EmailUnparsableError if from_address.blank?
+
+            create_issue!
+            send_thank_you_email!
+          end
+
+          private
+
+          def service_desk_key
+            @service_desk_key ||= (mail_key =~ /\Aservice-desk[+](\w+)\z/ and $1)
+          end
+
+          def project
+            return @project if instance_variable_defined?(:@project)
+
+            @project = Project.where(
+              service_desk_enabled: true,
+              service_desk_mail_key: service_desk_key
+            ).first
+          end
+
+          def create_issue!
+            # NB: the support bot is specifically forbidden
+            # from mentioning any entities, or from using
+            # slash commands.
+            @issue = Issues::CreateService.new(
+              project,
+              User.support_bot,
+              title: mail.subject,
+              description: message,
+              confidential: true,
+            ).execute
+
+            @issue.update_attributes(
+              service_desk_reply_to: from_address
+            )
+          end
+
+          def send_thank_you_email!
+            Notify.thank_you_email(@issue.id)
+          end
+
+          def from_address
+            (mail.reply_to || []).first || mail.sender || mail.from.first
+          end
+        end
+      end
+    end
+  end
+end