Adds noref/noopen to external links on admin integrations

Adds noref/noopen to external target=_blank links for Mailgun and
Snowplow in admin/application_settings/general

app/views/admin/application_settings/_mailgun.html.haml

@@ -8,7 +8,7 @@
     %button.btn.gl-button.btn-default.js-settings-toggle{ type: 'button' }
       = expanded ? _('Collapse') : _('Expand')
     %p
-      = _('Configure the %{link} integration.').html_safe % { link: link_to(_('Mailgun events'), 'https://documentation.mailgun.com/en/latest/user_manual.html#webhooks', target: '_blank') }
+      = _('Configure the %{link} integration.').html_safe % { link: link_to(_('Mailgun events'), 'https://documentation.mailgun.com/en/latest/user_manual.html#webhooks', target: '_blank', rel: 'noopener noreferrer') }
   .settings-content
     = form_for @application_setting, url: general_admin_application_settings_path(anchor: 'js-mailgun-settings'), html: { class: 'fieldset-form', id: 'mailgun-settings' } do |f|
       = form_errors(@application_setting) if expanded

app/views/admin/application_settings/_snowplow.html.haml

@@ -7,7 +7,7 @@
       = expanded ? _('Collapse') : _('Expand')
     %p
       - link_start = '<a href="%{url}">'.html_safe % { url: help_page_path('development/snowplow/index') }
-      = html_escape(_('Configure %{link} to track events. %{link_start}Learn more.%{link_end}')) % { link: link_to('Snowplow', 'https://snowplowanalytics.com/', target: '_blank').html_safe, link_start: link_start, link_end: '</a>'.html_safe }
+      = html_escape(_('Configure %{link} to track events. %{link_start}Learn more.%{link_end}')) % { link: link_to('Snowplow', 'https://snowplowanalytics.com/', target: '_blank', rel: 'noopener noreferrer').html_safe, link_start: link_start, link_end: '</a>'.html_safe }
   .settings-content
     = form_for @application_setting, url: general_admin_application_settings_path(anchor: 'js-snowplow-settings'), html: { class: 'fieldset-form', id: 'snowplow-settings' } do |f|
       = form_errors(@application_setting) if expanded