SG-38756 Fix parent property of PathTemplate in case of optional key

[ClementHector]

Context

The parent property of PathTemplate doesn't create a correct PathTemplate when optional keys are used. For example, if you create a template shots/{Sequence}[-{seq_num}]/{Shot}/{Step}/work, the parent property will return a templatePath without the optional [-{seq_num}] part.

Problem

When creating a PathTemplate with optional keys, the parent property omits these keys in the generated path. This can result in incorrect or incomplete paths.

Solution

To solve this issue, instead of passing self.definition to the PathTemplate constructor, we use self._repr_def, which contains the optional keys.

Testing

A test has been added to verify that the parent property now correctly includes optional keys in the generated PathTemplate.

[julien-lang]

Thanks for your contribution @ClementHector! We are going to review and test.

[ClementHector]

With pleasure @julien-lang , don't hesitate to ask me for corrections.