As uvicorn may be run with at maximum of 9 workers (because of the
number of connections to the database,) it may happen that one worker
starts the authentication process and another finishes it. However, the
global variable `tmp_auth_store` is not shared between these workers
(processes.)

This is fixed with storing temporary information to files.

This problem could be avoided by sticking with RESTful architecture.
However, authentication is challenging as OpenStreetMap use OAuth1 which
support only authorization. Therefore, for authentication purposes of
the damn server, RESTful architecture is broken.