Display subsciption reference in django administration.

coin/offers/admin.py

@@ -28,8 +28,8 @@ class OfferAdmin(admin.ModelAdmin):
 
 
 class OfferSubscriptionAdmin(admin.ModelAdmin):
-    list_display = ('member', 'offer', 'subscription_date', 'commitment',
-                    'resign_date')
+    list_display = ('display_subsciption_reference', 'member', 'offer',
+                    'subscription_date', 'commitment', 'resign_date')
     list_display_links = ('member','offer')
     list_filter = ( OfferSubscriptionTerminationFilter,
                     OfferSubscriptionCommitmentFilter,