Embedded editor in preview mode via `NcReferenceWidget` doesn't support attachments

[mejo-]

Describe the bug
The embedded editor in preview mode via NcReferenceWidget doesn't know about a fileId and therefore has not AttachmentsResolver. That results in attachments/images not being loaded.

To Reproduce
Steps to reproduce the behavior:

1. Create a Text document with an image
2. Add the internal link to this document to another Text document or a Talk conversation
3. If added to anoter Text document, turn the link into a preview
4. See error "Attachment source was not resolved"

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots

Server details:

• Nextcloud version: 30.0.0rc2

[juliusknorr]

We should have the file id available as the file reference widget passes it to our viewer component
https://github.com/nextcloud/server/blob/5b7dcc1427e996a3154761877d1e11463ed4bef4/apps/files/src/views/ReferenceFileWidget.vue#L149

So it might be just a matter of passing that along to the read only view in

text/src/components/ViewerComponent.vue

Line 20 in 3a9c4f6

<Component :is="readerComponent" :content="content" />

[mejo-]

Nice. We have to migrate from RichTextReader to MarkdownContentEditor in the ViewerComponent, but a quick text revealed it works. I'll open a PR.