Crosspost should copy body text and link to the original post for all post types, not just text-only

[DavidHiraki]

Is Your Feature Request Related to a Problem?

When crossposting a text-only post, Thunder automatically populates the body field with a link to the original post and quotes any existing body text. This is good.

When crossposting a URL or image post, the body field is empty. No link to the original post is added to the body field, nor is any body text quoted. This is not good.

Issue raised here: https://sh.itjust.works/post/24540591

Feature Description

When crossposting a URL or image post, Thunder should automatically populate the body field with a link to the original post and quote any existing body text.

Alternative Solutions

No response

Additional Context

Discussed here: https://lemmy.world/comment/12719015

There was at least one argument against this feature (wanting to change the contents of the cross-post to be relevant to the community to cross-post to), so it might be worth making this a user-configurable setting, though I think it should be enabled by default.