models: Add plan_name attribute to CustomerPlan.

corporate/models.py

@@ -66,6 +66,15 @@ class CustomerPlan(models.Model):
 
     # TODO maybe override setattr to ensure billing_cycle_anchor, etc are immutable
 
+    @property
+    def name(self) -> str:
+        return {
+            CustomerPlan.STANDARD: 'Zulip Standard',
+            CustomerPlan.PLUS: 'Zulip Plus',
+            CustomerPlan.ENTERPRISE: 'Zulip Enterprise',
+        }[self.tier]
+
+
 def get_current_plan_by_customer(customer: Customer) -> Optional[CustomerPlan]:
     return CustomerPlan.objects.filter(
         customer=customer, status__lt=CustomerPlan.LIVE_STATUS_THRESHOLD).first()

corporate/views.py

@@ -264,10 +264,6 @@ def billing_home(request: HttpRequest) -> HttpResponse:
             if new_plan is not None:  # nocoverage
                 plan = new_plan
             assert(plan is not None)  # for mypy
-            plan_name = {
-                CustomerPlan.STANDARD: 'Zulip Standard',
-                CustomerPlan.PLUS: 'Zulip Plus',
-            }[plan.tier]
             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
@@ -284,7 +280,7 @@ def billing_home(request: HttpRequest) -> HttpResponse:
                 payment_method = 'Billed by invoice'
 
             context.update({
-                'plan_name': plan_name,
+                'plan_name': plan.name,
                 'has_active_plan': True,
                 'free_trial': free_trial,
                 'downgrade_at_end_of_cycle': downgrade_at_end_of_cycle,