Simplifying the logic for setting the metadata. There should be three ways of setting user metadata:
The upload api/methods should be used if and only if the field in question is defined on the upload level. This currently includes the attributes
upload_time (changing the last two requires admin privileges). The upload api/method should also ensure that the fields that are mirrored to entry metadata are consistently copied to all entries (which was not ensured previously). Old storage of compressed metadata in pickled files is removed.