Task: add warning to "Needs revision" action if no file uploaded by coach

2 parts....

We've already added the confirmation to both the "needs revision" and the "submission accepted" coach buttons. There is no warning though about closing the return folder by clicking either button, which could be a problem if the coach still wanted to add a file, but wasn't aware of the workflow.

We should therefore at least add a notification/warning when the "Needs revision" button is clicked and uploaded/created files = 0 , along the lines of the warning users get when clicking final submission without documents.

In case of

• Return and feedback / Revision phase
• file uploaded / created = 0 by coach
• click on "Needs revision"

show warning (with yellow background)

DE:
Titel: Überarbeitung benötigt
Text: Mit dieser Aktion schliessen Sie den Rückgabeordner. Falls Sie noch ein Dokument zur Korrektur erstellen oder hochladen wollen, dann klicken Sie auf "Abbrechen"

En:
Title: Revision needed
Text: This will close the return box. If you wish to upload or create a feedback for this user, click "Cancel".

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textual modifications to coach notification:
the german wording in the coach notification titles (from OO-1690) are rather awkward. Please modify the following

Benötigt Überarbeitung
Old: Bestätigung der Überarbeitungsanforderung
New: Bestätigung: Überarbeitung angefordert

Revision akzeptiert
Old: Bestätigung der Annahme der Abgabe
New: Bestätigung: Abgabe akzeptiert