* Validate the grafana URL setting to ensure it is a valid URL and does
not contain javascript.
* Add a rel='noopener noreferrer' attribute to the link on the frontend
so that when the link is opened in a new tab, it will not be able to
control the tab from which it was opened.
* Use the system_hook_validator for grafana_url since it is an admin
setting.
* Add migration to remove any javascript URLs from
application_settings.grafana_url.
* Add a blocked_message option to addressable_url_validator. The option
allows a custom error message to be added if the URL is blocked.
* Add a parse_url method to Gitlab::Util which returns an
Addressable::URI object.
* Add changelog entry.