Unit test intervention forms

* adds unit test for new/edit intervention forms
* improves code base for generating new identifiers

intervention/models/intervention.py

@@ -14,7 +14,7 @@ from django.urls import reverse
 from django.utils import timezone
 
 from analysis.settings import LKOMPVZVO_PUBLISH_DATE
-from compensation.models import EcoAccountDeduction
+from intervention.settings import INTERVENTION_IDENTIFIER_LENGTH, INTERVENTION_IDENTIFIER_TEMPLATE
 from intervention.tasks import celery_export_to_egon
 from user.models import User
 from django.db import models, transaction
@@ -61,6 +61,9 @@ class Intervention(BaseObject,
 
     objects = InterventionManager()
 
+    identifier_length = INTERVENTION_IDENTIFIER_LENGTH
+    identifier_template = INTERVENTION_IDENTIFIER_TEMPLATE
+
     def __str__(self):
         return f"{self.identifier} ({self.title})"