custom save method implemented in ItemForm(); views & tests updated accordingly (all UTs & FTs passing)

src/apps/dashboard/forms.py

@@ -16,3 +16,7 @@ class ItemForm(forms.models.ModelForm):
             ),
         }
         error_messages = {"text": {"required": EMPTY_ITEM_ERROR}}
+
+    def save(self, for_list):
+        self.instance.list = for_list
+        return super().save()