billing: Create is_free_trial function in CustomerPlan model.

corporate/lib/stripe.py

@@ -136,7 +136,7 @@ def next_month(billing_cycle_anchor: datetime, dt: datetime) -> datetime:
 
 
 def start_of_next_billing_cycle(plan: CustomerPlan, event_time: datetime) -> datetime:
-    if plan.status == CustomerPlan.FREE_TRIAL:
+    if plan.is_free_trial():
         assert plan.next_invoice_date is not None  # for mypy
         return plan.next_invoice_date
 
@@ -358,7 +358,7 @@ def make_end_of_cycle_updates_if_needed(
                 licenses=last_ledger_entry.licenses_at_next_renewal,
                 licenses_at_next_renewal=last_ledger_entry.licenses_at_next_renewal,
             )
-        if plan.status == CustomerPlan.FREE_TRIAL:
+        if plan.is_free_trial():
             plan.invoiced_through = last_ledger_entry
             assert plan.next_invoice_date is not None
             plan.billing_cycle_anchor = plan.next_invoice_date.replace(microsecond=0)

corporate/models.py

@@ -117,6 +117,9 @@ class CustomerPlan(models.Model):
             LicenseLedger.objects.filter(plan=self).order_by("id").last().licenses_at_next_renewal
         )
 
+    def is_free_trial(self) -> bool:
+        return self.status == CustomerPlan.FREE_TRIAL
+
 
 def get_current_plan_by_customer(customer: Customer) -> Optional[CustomerPlan]:
     return CustomerPlan.objects.filter(

corporate/views.py

@@ -300,7 +300,6 @@ def billing_home(request: HttpRequest) -> HttpResponse:
             if new_plan is not None:  # nocoverage
                 plan = new_plan
             assert plan is not None  # for mypy
-            free_trial = plan.status == CustomerPlan.FREE_TRIAL
             downgrade_at_end_of_cycle = plan.status == CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE
             switch_to_annual_at_end_of_cycle = (
                 plan.status == CustomerPlan.SWITCH_TO_ANNUAL_AT_END_OF_CYCLE
@@ -324,7 +323,7 @@ def billing_home(request: HttpRequest) -> HttpResponse:
             context.update(
                 plan_name=plan.name,
                 has_active_plan=True,
-                free_trial=free_trial,
+                free_trial=plan.is_free_trial(),
                 downgrade_at_end_of_cycle=downgrade_at_end_of_cycle,
                 automanage_licenses=plan.automanage_licenses,
                 switch_to_annual_at_end_of_cycle=switch_to_annual_at_end_of_cycle,
@@ -391,7 +390,7 @@ def update_plan(
             assert plan.fixed_price is None
             do_change_plan_status(plan, status)
         elif status == CustomerPlan.ENDED:
-            assert plan.status == CustomerPlan.FREE_TRIAL
+            assert plan.is_free_trial()
             downgrade_now_without_creating_additional_invoices(user.realm)
         return json_success()