Dynamic pricing for custom invoices

Some users might found Dynamic pricing of payments missleading
as normal access fee can be paid with dynamic pricing, but
reorrucing custom invoice recalls flat rate.

This commit changes custom invoice logic so that it allows
dynamic pricing. Minimium payment is calculated from service
minimum payment * service payment times.

It can be disabled from settings.py or constance admin panel

Signed-off-by: Erkki Hietaranta <erkki.hietaranta@gmail.com>

drfx/settings.py

@@ -21,6 +21,7 @@
 DEFAULT_ACCOUNT_SERVICE = 2
 
 CUSTOM_INVOICE_REFERENCE_BASE = 10000
+CUSTOM_INVOICE_DYNAMIC_PRICING = True
 SERVICE_INVOICE_REFERENCE_BASE = 20000
 
 MEMBERSHIP_APPLICATION_NOTIFY_ADDRESS = "example@example.com"
@@ -386,4 +387,5 @@
     # "ACCOUNT_IBAN": (ACCOUNT_IBAN, "IBAN of the association's bank account"),
     # "ACCOUNT_BIC": (ACCOUNT_BIC, "BIC of the association's bank account"),
     # "ACCOUNT_NAME": (ACCOUNT_NAME, "Name of the association's bank account"),
+    "CUSTOM_INVOICE_DYNAMIC_PRICING": (CUSTOM_INVOICE_DYNAMIC_PRICING, "Allow dynamic pricing when paying with custom invoice", bool)
 }

users/models/custom_invoice.py

@@ -65,3 +65,8 @@ def __str__(self):
             "amount": self.amount,
             "reference": self.reference_number,
         }
+
+    # cost is used if not set
+    def cost_min(self):
+       cm = self.days / self.subscription.service.days_per_payment * self.subscription.service.cost_min
+       return cm

utils/businesslogic.py

@@ -289,7 +289,9 @@ def _check_transaction_pays_custominvoice(transaction):
         )
 
         for invoice in invoices:
-            if transaction.amount >= invoice.amount:
+            #if transaction.amount >= invoice.amount:
+            invoice_cost_min = invoice.cost_min()
+            if config.CUSTOM_INVOICE_DYNAMIC_PRICING and transaction.amount >= invoice_cost_min or transaction.amount >= invoice.amount:
                 subscription = ServiceSubscription.objects.get(
                     user=invoice.user, id=invoice.subscription.id
                 )
@@ -431,7 +433,7 @@ def _service_paid_by_transaction(servicesubscription, transaction, add_days):
                 else:
                     extra_days = timedelta(
                         #Calculate child subscription payment to happen same time that latest parrent subsciption,
-                        #useful with custominvoices that pays subsription multiple times
+                        #useful with custominvoices that pays Parent subscription multiple times
                         days = add_days - servicesubscription.service.days_per_payment + paid_servicesubscription.service.days_per_payment
                     )
                     paid_servicesubscription.paid_until = transaction.date + extra_days