add possibility to specify a maturity date

for the membership fees

association.py

 # This file is part of Tryton. The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 from decimal import Decimal
+from datetime import timedelta
 from trytond.config import config
 from trytond.i18n import gettext
 from trytond.model import Workflow, ModelView, ModelSQL, fields, Unique
@@ -286,6 +287,9 @@ class MembershipType(ModelSQL, ModelView):
         required=True,
         ondelete='RESTRICT',
         help="The revenue account that is used for the fee.")
+    maturity_delay = fields.TimeDelta("Maturity Delay",
+        required=True,
+        help="The period of time after the membership fees must be paid")
     company = fields.Many2One('company.company', 'Company', required=True,
         select=True,
         domain=[
@@ -298,6 +302,10 @@ class MembershipType(ModelSQL, ModelView):
     def default_company(cls):
         return Transaction().context.get('company')
 
+    @classmethod
+    def default_maturity_delay(cls):
+        return timedelta(0)
+
 
 class Membership(ModelSQL, ModelView):
     """Membership"""
@@ -617,13 +625,15 @@ class Fee(ModelSQL, ModelView):
         party = None
         if account.party_required:
             party = self.member.party
-        else:
-            party = None
+
+        maturity_date= self.period.start_date + \
+            self.period.membership_type.maturity_delay
 
         return MoveLine(
             debit=abs(amount) if amount > 0 else 0,
             credit=abs(amount) if amount < 0 else 0,
             account=account,
+            maturity_date=maturity_date,
             party=party,
         )
 

view/membership_type_form.xml

@@ -14,6 +14,8 @@ this repository contains the full copyright notices and license terms. -->
             <field name="account_revenue" />
             <label name="journal" />
             <field name="journal" />
+            <label name="maturity_delay" />
+            <field name="maturity_delay" />
         </page>
     </notebook>
 </form>
\ No newline at end of file