Reports without report items should be considered as failed

Background:

Currently, for several reasons reports appear in the system that seem to be "empty", but are marked as successfully harvested.

This is caused e.g. by providers that do not comply exactly to the standard, because they include a report header with an exception message. So instead of displaying the error message like "No valid customer id", Folio stores the report according to the information provided in the header and handles it as successfully harvested. 

As a result, the user can never be sure if a report marked as successfully harvested really has been downloaded.

As the eUsage havester directly relies on the sushi specification, there is no sensible way to handle such incorrect reports. Users should contact the provider.

Scope:

The harvester should validate a report before saving, to make sure that at least one report item is included.

If the report does not contain any report items, it should be handled as failed, flagged accordingly and provide an error info message like "No report items."