Removing the cover from your profile does not federate out

[jwr1]

Describe the bug
When I remove the cover from my user profile, it seems like the change is not federated out. If I set the cover, it shows on fedia.io for example, but if I then remove it, the cover is still displayed on fedia.io (same for other instances as well).

On which Mbin instance did you find the bug?
kbin.earth

Which Mbin version was running on the instance?
1.8.0

To Reproduce
Not sure if there's a way to remove the cover through the Mbin web client, but I know you can through the API.

1. With Interstellar, open the Account page.
2. Click on the Overview tab.
3. Click Edit account profile.
4. Click the trash button at the very top that is displayed over the account cover image.
5. Click Save changes.

From there, you should see that your cover image is indeed removed locally, but it is still present on remote servers.

[jwr1]

I wonder if the same issue is present with profile avatars as well.

[BentiGorlich]

So I did a little digging: no Update activity is federated out directly (will fix) and users cannot just delete the avatar or cover (will also fix).

That being said, as and mbin do not only work user<->user, the user information will be refetched when needed. In our case that means if we receive an activity from a user and the last refresh of this user was more than 24h ago.

As we do have user follows the followers of a user should be notified