Allow tenant-specific defaults for inventory integration

Overview:
MODORDERS-178 added two enumeration fields used to control which types of inventory records should be created for both physical and electronic orders, including system-wide defaults. Once that's in place, we need to allow tenants to specify their own tenant-specific defaults, which would override the more generic system-wide defaults.

In the UI, these would be set in the orders section of settings. On the backend the values would be stored mod-configuration. Both ui-orders and mod-orders might need to retrieve these settings. UI orders would retrieve them in order to set the default value in each of the drop-downs. Mod-orders would only need to read these settings if a value is not specified in order to determine what to use as a default. In both cases, if mod-configuration doesn't contain an entry for the tenant, the system-wide defaults should be used. The UI work will be tracked in a separate story.

Acceptance Criteria:

• the tenant-specific values are retrieved from mod-configuration as needed
• If no value exists in mod-configuration, the previously defined system-wide defaults are used.
• 80%+ test coverage on new code
• API Tests are updated to exercise this