LIMS-1113: Shipping service dispatch redirect - #698

JIRA ticket: LIMS-1113

Summary:
Adds the option to redirect to the shipping service to book shipments when requesting dispatch of appropriate Dewars.

Changes:

• Adds feature flag $use_shipping_service_redirect which enables/disables this feature
• On requesting Dewar dispatch, create a shipment request in the shipping service and redirect to the appropriate shipment workflow to book a shipment
• Use minimised dispatch request email for shipments booked via the new pathway

To test:

• Check that the appropriate dispatch form is displayed for academic, industrial, international users
• Check that the appropriate shipment request is created in the shipping service when requesting dispatch of a domestic academic Dewar
• Check that the minified dispatch-lite email template is used for such dispatch requests; ensure this has an appropriate link to where a Goods Handling operative can view and print the air waybill
• Check that the dispatch button links to the shipping service once a dispatch shipment request has been successfully created.