Unit test intervention forms

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

intervention/tests/unit/__init__.py

@@ -0,0 +1,7 @@
+"""
+Author: Michel Peltriaux
+Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
+Contact: ksp-servicestelle@sgdnord.rlp.de
+Created on: 24.08.23
+
+"""