allow end users to restart postprocessing

[butonic]

Is your feature request related to a problem? Please describe.

When a user sees this in his web view, a file is likely stuck in postprocessing:

He currently has to contact support / an administrator.

Describe the solution you'd like

I think it would be ok to let end users click the circle arrows to restart/resume the postprocessing for it.

Describe alternatives you've considered

I am just annoyed of having to go to the CLI and look through the upload session to find the right one to fix this.

Additional context

I think there is no harm in letting end users restart the postprocessing for a file. We could use a timeout before activation the acton in the web ui ... or we set a proper postprocessing status on the file.