feat(core): call models clean method prior to saving model to DB

ref: #426 #433

app/core/mixin/history_save.py

@@ -172,6 +172,8 @@ class SaveHistory(models.Model):
         is the data that was saved to the DB.
         """
 
+        self.clean()
+
         before = {}
 
         try:

docs/projects/centurion_erp/development/models.md

@@ -52,6 +52,8 @@ All models must meet the following requirements:
 
 - Attribute `table_fields` is defined with the fields to display by default for viewing the model within a table.
 
+- `clean()` method within a model is **only** used to ensure that the data entered into the DB is valid and/or to ensure application wide changes/validation is conducted prior to saving model.
+
 
 ## Checklist