Add server URL to notification template context

[jmbrunskill]

Is your feature request related to a problem? Please describe

Right now when you receive an email, it's not easy to tell which server it has come from, and would be very useful to be able to provide a link to the notification config in case you want to edit/update/disable it.

In future this could be extended to be an unsubscribe link...

Describe the solution you'd like

A new parameter is added to the tera context based on the server URL.
Probably best if there was a parameter something like notification_config_url that would contain something like

https://test-notify.msupply.org/notification/{NOTIFICATION_CONFIG_ID}

Acceptance Criteria

• It's possible to create a link to the notification config from within an Scheduled Notification template

Describe alternatives you've considered

Email headers do actually contain some information that can be used to traceback the server.
e.g.

Additional context