[BUG][Python] Tests should be generated under the PythonSrcRoot

Created by: tray2100

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The current behaviour is that tests are generated at the root directory even if pythonSrcRoot has been specified. At the very least the tests folder (and the files therein) should be generated under the pythonSrcRoot. This makes even more sense if you're also including pythonSrcRoot in the import namespace.

openapi-generator version

5.1.1

Suggest a fix

The fix here would be to modify the testPackage variable based on a flag if pythonSrcRoot has been specified to include the pythonSrcRoot value.