stripe: Rename CustomerPlan.is_paid.

This might not be the most meaningful change of phrasing, but .is_paid()
sounds like it's a check for whether the customer has already paid their
invoice. is_a_paid_plan() reflects better the meaning that it's whether
it's a plan of a "paid" type.

corporate/lib/stripe.py

@@ -2981,10 +2981,10 @@ class BillingSession(ABC):
             self.make_end_of_cycle_updates_if_needed(plan, event_time)
 
         # The primary way to not create an invoice for a plan is to not have
-        # any new ledger entry. The 'plan.is_paid()' check adds an extra
+        # any new ledger entry. The 'plan.is_a_paid_plan()' check adds an extra
         # layer of defense to avoid creating any invoices for customers not on
         # paid plan. It saves a DB query too.
-        if plan.is_paid():
+        if plan.is_a_paid_plan():
             if plan.invoicing_status == CustomerPlan.INVOICING_STATUS_INITIAL_INVOICE_TO_BE_SENT:
                 invoiced_through_id = -1
                 licenses_base = None
@@ -5174,7 +5174,9 @@ def invoice_plans_as_needed(event_time: Optional[datetime] = None) -> None:
                 plan.reminder_to_review_plan_email_sent = True
                 plan.save(update_fields=["reminder_to_review_plan_email_sent"])
 
-            free_plan_with_no_next_plan = not plan.is_paid() and plan.status == CustomerPlan.ACTIVE
+            free_plan_with_no_next_plan = (
+                not plan.is_a_paid_plan() and plan.status == CustomerPlan.ACTIVE
+            )
             free_trial_pay_by_invoice_plan = plan.is_free_trial() and not plan.charge_automatically
             last_audit_log_update = remote_server.last_audit_log_update
             if not free_plan_with_no_next_plan and (

corporate/models.py

@@ -476,7 +476,7 @@ class CustomerPlan(AbstractCustomerPlan):
     def is_free_trial(self) -> bool:
         return self.status == CustomerPlan.FREE_TRIAL
 
-    def is_paid(self) -> bool:
+    def is_a_paid_plan(self) -> bool:
         return self.tier in self.PAID_PLAN_TIERS