billing: Make source optional when creating stripe customer.

stubs/stripe/__init__.pyi

@@ -19,7 +19,7 @@ class Customer:
 
     @staticmethod
     def create(description: str, email: str, metadata: Dict[str, Any],
-               source: str) -> Customer:
+               source: Optional[str]) -> Customer:
         ...
 
     @staticmethod

zilencer/lib/stripe.py

@@ -136,7 +136,7 @@ def extract_current_subscription(stripe_customer: stripe.Customer) -> Any:
     return None
 
 @catch_stripe_errors
-def do_create_customer_with_payment_source(user: UserProfile, stripe_token: str) -> stripe.Customer:
+def do_create_customer(user: UserProfile, stripe_token: Optional[str]=None) -> stripe.Customer:
     realm = user.realm
     # We could do a better job of handling race conditions here, but if two
     # people from a realm try to upgrade at exactly the same time, the main
@@ -154,6 +154,7 @@ def do_create_customer_with_payment_source(user: UserProfile, stripe_token: str)
         RealmAuditLog.objects.create(
             realm=user.realm, acting_user=user, event_type=RealmAuditLog.STRIPE_CUSTOMER_CREATED,
             event_time=event_time)
+        if stripe_token is not None:
             RealmAuditLog.objects.create(
                 realm=user.realm, acting_user=user, event_type=RealmAuditLog.STRIPE_CARD_ADDED,
                 event_time=event_time)
@@ -231,7 +232,7 @@ def do_subscribe_customer_to_plan(stripe_customer: stripe.Customer, stripe_plan_
 def process_initial_upgrade(user: UserProfile, plan: Plan, seat_count: int, stripe_token: str) -> None:
     customer = Customer.objects.filter(realm=user.realm).first()
     if customer is None:
-        stripe_customer = do_create_customer_with_payment_source(user, stripe_token)
+        stripe_customer = do_create_customer(user, stripe_token=stripe_token)
     else:
         stripe_customer = do_replace_payment_source(user, stripe_token)
     do_subscribe_customer_to_plan(

zilencer/tests/test_stripe.py

@@ -17,7 +17,7 @@ from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.timestamp import timestamp_to_datetime, datetime_to_timestamp
 from zerver.models import Realm, UserProfile, get_realm, RealmAuditLog
 from zilencer.lib.stripe import catch_stripe_errors, \
-    do_create_customer_with_payment_source, do_subscribe_customer_to_plan, \
+    do_subscribe_customer_to_plan, \
     get_seat_count, extract_current_subscription, sign_string, unsign_string, \
     get_next_billing_log_entry, run_billing_processor_one_step, \
     BillingError, StripeCardError, StripeConnectionError