pac paportal download does not set previously populated fields to null

This issue is occurring when running CLI Version: 1.26.5+g670cdf9 via VS Code.

When pac paportal downloading a web page that used to have an adx_webform set but is now null, the key value pair is removed from the yaml file, so when deployed to other environments using pac paportal upload, the value in those environments is not cleared. A workaround we have been doing is when clearing a value from a web page and downloading the yaml, readding the key value pair and setting it to null. These fields not being cleared results in an error when viewing these pages as two copies of the same webform are trying to be rendered. This is because the Basic Form field in the environment had not been cleared, but the new code to render the basic form using liquid was also present.

A solution to this would be to keep the key value pairs in the yaml but set them to null when null in the source environment.

Start at the implementation of the pac paportal download and upload commands, tracing how source values are serialized into and read from YAML. Reproduce a page field changing from a populated adx_webform to null, then verify that the downloaded YAML preserves the key with a null value and that upload clears the destination field.