It's now in a state where it can actually upload ... something (that should work). Not tested the restore yet.
I did run into trouble with the max concurrent requests, which I had to up to [more than 4, now on 8] to get it to work -- I'm not sure if I'm just working around a bug here, or if that's expected behaviour.
part of CURA-12156
Converted doxygen style comments to reStructuredText style in the files found in Cura/cura/API directory recursively using the script dox_2_rst.py (provided in the Uranium repo). Comments were manually checked and changed if needed.
Comments from the hidden attributes in the class CuraAPI (_acount, _backups, _interface) were moved to the public property getters, so they docstrings are exposed to the user.