Ability to prevent thumbnails for attachments

[meeoh]

Is your feature request related to a problem? Please describe.
I have a model that has_many_attached some files. Those files are also encrypted. When an image is uploaded to that field and rails_admin tries to display the thumbnail, its using the resize variant which throws an error for encrypted files.

Describe proposed solution(s)
The ability to prevent images trying to be displayed for a certain field. If I can override image? or resource_url in the ActiveStorageAttachment class here that would allow me to disable showing images at all for this field and instead just show text which links to the document