[bug] CA/Cert creation generates 2 SQL write queries instead of 1

[nemesifier]

This code:

django-x509/django_x509/base/models.py

Lines 206 to 217 in c5a5acd

	def save(self, *args, **kwargs):
	generate = False
	if not self.pk and not self.certificate and not self.private_key:
	generate = True
	super().save(*args, **kwargs)
	if generate:
	# automatically determine serial number
	if not self.serial_number:
	self.serial_number = self._generate_serial_number()
	self._generate()
	kwargs['force_insert'] = False
	super().save(*args, **kwargs)

Generates two queries for creating a certificate and a CA.

I figured this out while working on openwisp/openwisp-controller#455.

I think this part could be optimized.

[SitaGanesh]

Hi Sir, I'm new to contributing to this project, but I'm eager to join your organization and excited to help out!

I've looked into the issue and believe the root cause is the redundant super().save calls in the save method. To optimize this, we can:

• This defers the initial super().save call until after generating the certificate and private key.
• Remove the second super().save call, as it's no longer necessary.

This will reduce database writes and ensure data consistency.

I'm going to dive into a PR to implement this change. Let me know if you have any suggestions.