feat: make subscription license provisioning eventually consistent

ENT-8269

license_manager/apps/subscriptions/admin.py

@@ -34,6 +34,7 @@
     SubscriptionPlan,
     SubscriptionPlanRenewal,
 )
+from license_manager.apps.subscriptions.tasks import provision_licenses_task
 
 
 def get_related_object_link(admin_viewname, object_pk, object_str):
@@ -334,10 +335,13 @@ def save_model(self, request, obj, form, change):
         customer_agreement_catalog = obj.customer_agreement.default_enterprise_catalog_uuid
         obj.enterprise_catalog_uuid = (obj.enterprise_catalog_uuid or customer_agreement_catalog)
 
-        # Create licenses to be associated with the subscription plan after creating the subscription plan
-        num_new_licenses = form.cleaned_data.get('num_licenses', 0) - obj.num_licenses
+        # Set desired_num_licenses which will lead to the eventual creation of those licenses.
+        obj.desired_num_licenses = form.cleaned_data.get('num_licenses', 0)
+
         super().save_model(request, obj, form, change)
-        SubscriptionPlan.increase_num_licenses(obj, num_new_licenses)
+
+        # Kick off the asynchronous process to provision licenses.
+        provision_licenses_task.delay(subscription_plan_uuid=obj.uuid)
 
 
 @admin.register(CustomerAgreement)

license_manager/apps/subscriptions/models.py

@@ -434,6 +434,17 @@ class SubscriptionPlan(TimeStampedModel):
         )
     )
 
+    desired_num_licenses = models.PositiveIntegerField(
+        blank=True,
+        null=True,
+        verbose_name="Desired Number of Licenses",
+        help_text=(
+            "Total number of licenses that should exist for this SubscriptionPlan. "
+            "The total license count (provisioned asynchronously) will reach the desired amount eventually. "
+            "Empty (NULL) means no attempts will be made to asynchronously provision licenses."
+        ),
+    )
+
     @property
     def days_until_expiration(self):
         """