Communication: Referencing lecture attachments in editor creates a link that cannot be accessed

[PaRangger]

Describe the bug

If you reference a lecture attachment in the markdown editor and create a post, then click on the link, it will give you a 404. The attachment itself however works, since you can view it in the lecture itself.

To Reproduce

1. Go to course
2. Go to the communication tab
3. Create a post and reference a lecture attachment
4. Click the link
5. Server returns a 404

Expected behavior

As in the lecture itself, the link should forward you to the file.

Screenshots

Which version of Artemis are you seeing the problem on?

7.7.4

What browsers are you seeing the problem on?

Chrome

Additional context

No response

Relevant log output

No response