fix: create CEA object when enrolling using a license flow [PALM]

[0x29a]

Description

This fix is similar to #14, but it's for license-based enrollment flow.

Testing steps

Follow testing steps from #14 up until Add a ledger here step. Be sure to use open-craft/edx-platform#656 branch for edx-platform during the devstack setup. Then:

1. Register some test user.
2. Note a UUID of some enterprise customer and its enterprise catalog.
3. Add an agreement here: http://localhost:18170/admin/subscriptions/customeragreement/ using UUIDs from №2.
4. Add a subscription here: http://localhost:18170/admin/subscriptions/subscriptionplan/ using UUIDs from №2. You can specify these details:

   Is active: check.
   Number of Licenses: 200.
   Salesforce opportunity line item: `00kNFJHRVSD683NDI8`.
   Product: `B2B Paid`.
   Should auto apply licenses: `Yes`.
   Reason for change: `New Subscription`.
   

5. The previous step should create 200 licenses here: http://localhost:18170/admin/subscriptions/license/. Choose one of them, set it to be Activated and set LMS user ID to the ID of the user you created in №1.
6. You may also need to add an assignment here: http://localhost:18160/admin/catalog/enterprisecatalogroleassignment/

   email: license_manager_worker@example.com
   role: enterprise_catalog_admin
   applies_to_all_contexts: true
   

7. Now add the test user to the chosen enterprise customer with an invitation-only course in its catalog and try enrolling this user to this course via the enterprise learner portal MFE.