Allow uploading of empty files

[plyhun]

Abstract

Allow Mesh to upload and publish empty (size == 0 bytes) files. This feature is asked by the storage automation workflow.

Checklist

• [x] Correctly process ZeroByteFileException

General

• [x] Added abstract that describes the change
• [x] Added changelog entry to /CHANGELOG.adoc
• [x] Ensured that the change is covered by tests
• [x] Ensured that the change is documented in the docs

On API Changes

• [ ] Checked if the changes are breaking or not
• [x] Added GraphQL API if applicable
• [x] Added Elasticsearch mapping if applicable