Detect and avoid missing Warehouses when creating orders

[jhoule86]

Main Fixes

• Filters out invalid Warehouse IDs when Orders are created

  • (ex: Warehouse is deleted but mapping in Wayfair plugin UI was not manually removed by user)

• Fixes https://github.com/wayfair-contribs/plentymarkets-plugin/issues/197 (regression) by adding a getter for the logger in Repository and repairing its child classes to use the getter when logging errors.

Testing Efforts

• Tests around Warehouse-Supplier mapping lookups
• Tests around order creation
• Tests around warehouse lookups

Code Health

• Break out some of the create logic in CreateOrderService into tested, mockable subroutines
• Remove return type restriction for method getOrderReferrerValue of AbstractConfigHelper / ConfigHelper because presence of Wayfair's Order Referrer is not 100% guaranteed, use a float|null type hint instead.
• Rename most variables in CreateOrderService to disambiguate them and to imply namespace (plenty vs wf)
• Rename query result variables to results instead of mapping, to improve code readability
• Add some comments about the fact that we need to do more detailed filtering on the Warehouse for an order, as mentioned in https://github.com/wayfair-contribs/plentymarkets-plugin/issues/92.