This change adds the initial implementation of the new API server in Kotlin,
replacing the old API written in Python. The implementation uses Quarkus,
RESTEasy, and Hibernate to implement the new API endpoints.

The reason for replacing the old API server is unifying the build and
deployment toolchains, reducing the number of technologies necessary to
work with OpenDC. Furthermore, we envision bundling the entire OpenDC
project into a single distributions, allowing users to launch their own
deployment trivially.

This change updates the deployment guide to include instructions on
configuring Auth0 for OpenDC. This process should not be much more
difficult than creating the Google Application.

This change updates the OpenDC API to use Auth0 for API authorization.
This removes the hard dependency on Google for logging into OpenDC and
simplifies implementation as we do not have to store user information
anymore, other than the user identifier.

This change removes the Socket.IO endpoint from the public API now that
we have switched to the REST API instead. This decreases the possible
exposure to vulnerabilities as well as the maintenance burden.

This change updates the project documentation by moving most of the
documentation to the docs directory.

This change updates the project structure to become flattened.
Previously, the simulator, frontend and API each lived into their own
directory.

With this change, all modules of the project live in the top-level
directory of the repository. This should improve discoverability of
modules of the project.