Django field validation before save

gistfile1.txt

- Django does not automatically check max_lenght limitation before save()
- Django does not automatically check choices before save() --> it's for form

for the length limitation, using

datamodel.full_clean()
datamodel.save()

can resolve it. or, override save() to enforce full_clean()
ex:
```python
def save(self, force_insert=False, force_update=False):
    self.full_clean()
    models.Model.save(self, force_insert, force_update)
```

for the choices validation issue, override save() to enforce validation of specific field to match choices.
ex:
```python
def save(self, force_insert=False, force_update=False, *args, **kwargs):
        valid_categories = [v[0] for v in InformationDislike.DISLIKECHOICE]
        if self.category not in valid_categories:
            raise IntegrityError("Invalid value %s for category field. The available values are %s"\
                                 % (self.category, valid_categories))
        models.Model.save(self, force_insert, force_update, *args, **kwargs)
```