Add BEFORE_CLEAN / AFTER_CLEAN hooks to support validation events

[konradbeck-creditech]

Description:
Allow django-lifecycle to register hooks around model validation by firing new events when Model.full_clean() or clean() runs.

Motivation:

• Validation in clean() today must be wired by hand, losing override benefits of lifecycle hooks.
• Form/Admin calls full_clean() under the hood—it’d be valuable to have BEFORE_CLEAN/AFTER_CLEAN events so errors integrate seamlessly with Django’s validation pipeline.

Proposal:

1. Define two new events (BEFORE_CLEAN, AFTER_CLEAN) in the priority module.
2. Wrap Model.full_clean() (or inside Model.clean()) to run those hooks before/after validation:

def full_clean(self, *args, **kwargs):
    self._run_hooks(BEFORE_CLEAN)
    super().full_clean(*args, **kwargs)
    self._run_hooks(AFTER_CLEAN)

3. Update docs to show how to use @hook(BEFORE_CLEAN) and @hook(AFTER_CLEAN) for modular validation.

@hook(BEFORE_CLEAN)
def normalize_phone(self):
    self.phone = clean_number(self.phone)

@hook(AFTER_CLEAN)
def check_business_rules(self):
    if self.quantity < 0:
        raise ValidationError({"quantity": "must be positive"})

Happy to help iterate on details or a PR!

[mrpawan-gupta]

@konradbeck-creditech Thanks for raising this — the idea around full_clean() hooks makes a lot of sense.

I’m new to contributing here, so just wanted to check if adding BEFORE_CLEAN / AFTER_CLEAN events and wiring them around Model.full_clean() aligns with the project’s direction.

If so, @@rsinger86 / @EnriqueSoria I’d be happy to try a PR with tests and docs and iterate based on feedback. Thanks!