Use logger.warning instead of logger.error for validation errors

[tnagorra]

No description provided.

[susilnem]

I think it also used to create multiple issues in Sentry!

[subinasr]

@tnagorra Is there a reason we're using warnings for transformation failures as well?

[tnagorra]

After implementing support for partial success, there can be a flood of transformation errors.
If we use logger.error, all of these are sent to Sentry and this can easily overwhelm the infrastructure (also introduce noise)

logger.warning is not sent to Sentry and we can refer to the logs for transformation errors