replace string with enum

fet2020/finance/admin.py

@@ -308,7 +308,7 @@ class BillAdmin(admin.ModelAdmin):
 
     @admin.display(description="QR Code")
     def get_qrcode(self, obj):
-        if obj.status != "C":
+        if obj.status != Bill.Status.CLEARED:
             return "-"
 
         try:
@@ -335,10 +335,10 @@ class BillAdmin(admin.ModelAdmin):
     def status_colored(self, obj):
         # TODO: if there is a status without color, set nothing.
         colors = {
-            "S": "red",
+            Bill.Status.SUBMITTED: "red",
-            "C": "darkorange",
+            Bill.Status.CLEARED: "darkorange",
-            "F": "green",
+            Bill.Status.FINISHED: "green",
-            "I": "blue",
+            Bill.Status.INCOMPLETED: "blue",
         }
         return format_html(
             f'<b style="background:{colors[obj.status]};">{obj.get_status_display()}</b>'
@@ -346,7 +346,7 @@ class BillAdmin(admin.ModelAdmin):
 
     @admin.action(description="Als 'Abgerechnet' markieren.")
     def make_cleared(self, request, queryset):
-        updated = queryset.update(status="C")
+        updated = queryset.update(status=Bill.Status.CLEARED)
         self.message_user(
             request,
             ngettext(
@@ -360,7 +360,7 @@ class BillAdmin(admin.ModelAdmin):
 
     @admin.action(description="Als 'Abgeschlossen' markieren.")
     def make_finished(self, request, queryset):
-        updated = queryset.update(status="F")
+        updated = queryset.update(status=Bill.Status.FINISHED)
         self.message_user(
             request,
             ngettext(