feat(api): api update (#478)

.stats.yml

@@ -1,2 +1,2 @@
 configured_endpoints: 101
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/orb%2Forb-b6d60f8edbdc94e65f06b0b002cc8e1f27aceccc67917bea849425701ba82fb8.yml
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/orb%2Forb-52bd3046e73f201c4d08edfa92756791c015be907691a7893f8e7782cc2aea6f.yml

src/orb/types/invoice.py

@@ -927,11 +927,8 @@ class Invoice(BaseModel):
 
     discounts: List[InvoiceLevelDiscount]
 
-    due_date: Optional[datetime] = None
-    """When the invoice payment is due.
-
-    The due date is null if the invoice is not yet finalized.
-    """
+    due_date: datetime
+    """When the invoice payment is due."""
 
     eligible_to_issue_at: Optional[datetime] = None
     """

src/orb/types/invoice_fetch_upcoming_response.py

@@ -927,11 +927,8 @@ class InvoiceFetchUpcomingResponse(BaseModel):
 
     discounts: List[InvoiceLevelDiscount]
 
-    due_date: Optional[datetime] = None
-    """When the invoice payment is due.
-
-    The due date is null if the invoice is not yet finalized.
-    """
+    due_date: datetime
+    """When the invoice payment is due."""
 
     eligible_to_issue_at: Optional[datetime] = None
     """