Add-on Make a resource icon from the first attachment XF1

[Robert9]

I need an addon that:

takes the first attachment of a new added resource and create a resource icon with these rules:

1. when add a resource
2. when there is at least one attached image
3. when there is no hotlinked image

=> than take the first attached image and make a thread icon
Parts of the code for making the icon itself is ready to use. I use it in another addon.

And again:
Dont make an icon,
- when edit the resource
- when there is a hotlinked image
- when there is no attached image