Mailer to deliver issues csv as attachment

app/mailers/emails/issues.rb

@@ -49,6 +49,13 @@ module Emails
       mail_answer_thread(issue, issue_thread_options(updated_by_user.id, recipient.id))
     end
 
+    def issues_csv_email(user, project, content)#, issues) file_name: or content: or issues:
+      @project = project
+
+      attachments['issues.csv'] = { content: content, mime_type: 'text/csv' }
+      mail(to: user.notification_email, subject: subject("Issues exported as CSV"))
+    end
+
     private
 
     def setup_issue_mail(issue_id, recipient_id)

app/views/notify/issues_csv_email.html.haml

+%p
+  Your issues for #{@project.name} have been attached as a CSV.
\ No newline at end of file

app/views/notify/issues_csv_email.text.erb

+Your issues for <%= @project.name %> have been attached as a CSV.
\ No newline at end of file

spec/mailers/emails/issues_spec.rb

+require 'spec_helper'
+require 'email_spec'
+require 'mailers/shared/notify'
+
+describe Notify do
+  include EmailSpec::Matchers
+  include_context 'gitlab email notification'
+
+  describe 'csv export email' do
+    let(:user) { create(:user) }
+    let(:empty_project) { create(:empty_project) }
+    subject { Notify.issues_csv_email(user, project, "dummy content") }
+
+    it 'attachment has csv mime type' do
+      attachment = subject.attachments.first
+      expect(attachment.mime_type).to eq 'text/csv'
+    end
+  end
+end

spec/mailers/previews/issues_csv_mailer_preview.rb

+class IssuesCsvMailerPreview < ActionMailer::Preview
+  def issues_csv_export
+    user = OpenStruct.new(notification_email: 'a@example.com')
+    project = OpenStruct.new(name: 'Judolint')
+
+    Notify.issues_csv_email(user, project, "Dummy,Csv\n0,1")
+  end
+end