copySolutions demo doesn't copy thumbnail

[MikeTschudi]

Thanks to Johnny Chang,

groupCategories are searched using the categories param. Item categories is not searchable using this endpoint. This is laid out in the doc but it might be good to further emphasize this as we are reusing the categories field as people would probably assume they’re searching the categories field rather than groupCategories

[MikeTschudi]

The presence or absence of groupCategories is a group configuration error, and so I'm switching the issue to focus on the missing thumbnail.

[MikeTschudi]

Setting the thumbnail appears to be an issue with the ArcGIS REST API.