[Feature request] Support no gui server?

[shenmishajing]

Now, we use PyQt to login, which requires the GUI interface. On a no GUI server, any command, not only the login command, will result in an error as follows since we try to import PySide6 at the top of olsync.py.

ImportError: /usr/lib/x86_64-linux-gnu/libwayland-server.so.0: undefined symbol: ffi_type_uint32, version LIBFFI_BASE_7.0

After reading the source code of ols, I find that the following information is enough for ols:

{
    "cookie": {
        "overleaf_session2": "xxx",
        "GCLB": "xxx"
    },
    "csrf": "xxx"
}

All those cookies and csrf can be found manually. So, we can ask the user to provide a json or a .oauth to login instead of requiring the pyqt package to open a browser.

A simple solution is as follows:

1. move the import olbrowserlogin statement from the top of olsync.py to the function login_handler.
2. use a json file as the .oauth instead of pickle file.

How do you think about this? Will we support this? I can create a PR for this if we want to add this feature.