* Added in models to track enterprise enrollment source and updated the Enterprise Course Enrollments and PendingEnrollments to track that source.
2.0.16
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* Address defect ENT-2463. Add protection within EnterpriseCustomerUser model in enroll method during course enrollments.
2.0.15
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* Added missing migration for EnterpriseCustomerUser
2.0.14
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* Add Enterprise selection page to allow a learner to select one of linked enterprises
2.0.13
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* Add manual order creation to enterprise manual enrollment admin form
2.0.12
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* Update 'EnterpriseCustomerUser' model. Add 'create_order_for_enrollment'. Called during 'enroll'. Will create an ecommerce order for pending course enrollments.