LIMS-2281: Simplify code between Synchweb and Shipping Service

[ndg63276]

JIRA ticket: LIMS-2281

Summary:

Remove the option to use the shipping service without redirection, so we can send the shipping service the external_id of null. This will get rid of the error when the same external_id gets reused for incoming and outgoing.

Changes:

• Remove config variables for redirecting to shipping service (assume true if shipping service in use)
• Remove else clauses that are no longer in use
• Remove _dispatch_dewar_in_shipping_service and _book_shipment_in_shipping_service functions that are no longer accessible
• Remove no longer used functions from ShippingService.php
• Send external_id of null to the shipping service, now it is no longer retrieved
• Remove unnecessary apostrophes in dispatch warnings

To test:

• Enable the shipping service in config

$use_shipping_service = True;
$use_shipping_service_incoming_shipments = True;
$shipping_service_app_url = "https://sample-shipping-test.diamond.ac.uk";

• Go to any proposal (eg mx23694), go to /shipments/add and create a UDC shipment using a UK lab contact, and clicking "Use Facility Account"

• Click Create DHL Air Waybill, then Proceed, then complete the shipping service form

• Check the AWB number ends up in ISPyB, and the dewar status goes to "awb created" or "pickup booked"

• Click "Dispatch" and then "Proceed", then complete the shipping service form

• Check the return AWB number ends up in ISPyB, and the dewar status goes to "dispatch-booked"

• Disable the shipping service in config

$use_shipping_service = False;
$use_shipping_service_incoming_shipments = False;

• Repeat the test, except this time it will be a Synchweb form rather than the shipping service