feat(api): get /api/user for public user details

feat(schema, shared, api): move all types to shared, separate schema
 * schema is now stored in a separate crate to avoid dependency cycles
 * added note in README.md about handling unwraps

feat(api): reimpl all_games and my_games

feat(api): stubs for most game endpoints, complete create

feat(client): init game handlers module

feat(api): create session on register

feat(api): logout endpoint

WIP(api): session management

feat(api): reimpl user registration

feat(api): reimpl /api/info