Export to DMS should show validation errors immediately

[matthias-ronge]

If the export to the DMS is carried out manually, a green message confirms that the export is now being carried out by the task manager. The message is also displayed if the validation at the beginning of the export fails . You have to visit the task manager to see if it actually worked.

Goal: The validation should take place immediately, and in the event of an error, the error should be displayed here. The transfer to the task manager should only take place after the validation was successful.