Adding attribute to a form produces attributes with invalid classid contents

[zdeneksrejber]

Summary

When using and agent to add an existing attribute to a form's XML, the generated <control> element uses a random value for classid. This results in the form XML being invalid and the field rendering incorrectly or not at all.

Such generated content can then pass via build without an issue

Suggested change

Add validation of classid values based on predetermined set. See https://blog.networg.com/2019/06/10/dynamics-365-custom-dialogs-in-uci-part-3/

[zdeneksrejber]

To repro, you can just manually edit any classid value to invalid one, then run build, no agent needs to be involved.