code: def create(self, validated_data):
          
          enterprise_customer = self.context.get('enterprise_customer')
          lms_user = validated_data.get('lms_user_id')
          tpa_user = validated_data.get('tpa_user_id')
          user_email = validated_data.get('user_email')
          course_run_id = validated_data.get('course_run_id')
          course_mode = validated_data.get('course_mode')
          cohort = validated_data.get('cohort')
          email_students = validated_data.get('email_students')
          is_active = validated_data.get('is_active')
  
          enterprise_customer_user = lms_user or tpa_user or user_email
  
          if isinstance(enterprise_customer_user, models.EnterpriseCustomerUser):
              validated_data['enterprise_customer_user'] = enterprise_customer_user
              try:
                  if is_active:
                      enterprise_customer_user.enroll(course_run_id, course_mode, cohort=cohort)
                  else:
                      enterprise_customer_user.unenroll(course_run_id)
              except (CourseEnrollmentDowngradeError, CourseEnrollmentPermissionError, HttpClientError) as exc:
                  validated_data['detail'] = str(exc)
                  return validated_data
  
              if is_active:
                  track_enrollment('enterprise-customer-enrollment-api', enterprise_customer_user.user_id, course_run_id)
          else:
              if is_active:
                  enterprise_customer_user = enterprise_customer.enroll_user_pending_registration(
                      user_email,
                      course_mode,
                      course_run_id,
                      cohort=cohort
                  )
              else:
                  enterprise_customer.clear_pending_registration(user_email, course_run_id)
  
          if email_students:
              enterprise_customer.notify_enrolled_learners(
                  self.context.get('request_user'),
                  course_run_id,
                  [enterprise_customer_user]
              )
  
          validated_data['detail'] = 'success'
  
          return validated_data
docs: Perform the enrollment for existing enterprise customer users, or create the pending objects for new users.