fix: exclude revision family from duplicate IPN check

[bvweerd]

When PART_ALLOW_DUPLICATE_IPN is False, saving a revision that shares the same IPN as its parent incorrectly raised a "Duplicate IPN not allowed" error. Revisions of the same part are expected to share the same IPN, so they must be excluded from the uniqueness check.

Fixes #12017

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[SchrodingersGat]

The PART_ALLOW_DUPLICATE_IPN option is intended to enforce global uniqueness of IPN values

[bvweerd]

But how is it then that you're allowed to make a revision item with the same IPN, although the allow duplicate IPN is false, but not unlock the part?

Looking at the code in validate_unique(), the model itself already has a check (line 1053) that explicitly allows the same IPN across different revisions, as long as the combination of Name + IPN + Revision is unique:

  if (self.revision or self.IPN) and (
      Part.objects.exclude(pk=self.pk)
      .filter(name=self.name, revision=self.revision, IPN=self.IPN)
      .exists()
  ):
      raise ValidationError('Part with this Name, IPN and Revision already exists.')

This check implicitly permits two parts to share the same IPN as long as their revision differs.

Also referring to #1112 (comment)

[matmair]

IMO: unique means unique; not unique together with another key