Closes #188 (closed)
Changed direct upload endpoint to return an id of the newly created submission
To be filled in by the reviewers
All of the methods are commented to expectation
The methods are tested to satisfaction
There are no unnecessary files present in the MR
The continuous integration has no problems with the MR
The MR is filled in as requested (including labels, milestones, and reviewers)
The documentation is up-to-date
All nullable parameters are marked as such