For now, only a basic implementation of OAuth with Discord is
implemented. If the user calls the Discord signin endpoint, they get
redirected to Discord’s OAuth page. Once they accept, they get
redirected back to the backend’s callback API endpoint. The token the
user got from Discord is stored in the user’s session.
When the user wants to log out, the user’s session’s token is wiped.
This commit also updates the dependencies of the project. It also
removes the dependency lettre as well as the mailpit docker service
for developers as it appears clearer this project won’t send emails
anytime soon.