User permissions for performance test command on linux

[KaloyanTanev]

🎯 Problem to be solved

Currently when charon test performance command is ran under Docker, the disk measurement tests work great for macOS. The way it works is that we create a volume in which a test file is written from inside of the Docker container. That is so we have more precise measurement as we measure the actual volume of the os, instead of the virtualised docker disk. This works great when ran under macOS, as the file sharing virtualisation framework (VirtioFS or even older ones) map the host user's uid and gid to the ones in the container. This way inside of the Docker container the user that writes to the mapped volume directory is as if it is the same user as the one in the host. However, under linux distro (currently tested is Debian) this is not the case. The user inside the container does not have permissions to write in the directory. This should be fixed, so that we can use the test command under linux machines.

🛠️ Proposed solution

Review the main charon Dockerfile, currently we hardcode the UID and GID, assuming 1000. It was introduced as a bit of a dirty fix more than 2 years ago - 798cba9. It would be much better if we accept env variables of UID and GID passed or default to 1000.

🧪 Tests

• Test if the charon test performance command works under debian for user and usergroup different than 1000.