Replaced the ApiKey concept with ephemeral tokens. Users and apps obtain a
token by authenticating the user credentials (to be implemented). The service
then generates a temporary token that is stored by the client and sent with
every request using the `Authorization-Token` header. The server verifies this
token to recognize and authenticate the request. With an authenticated user,
the server can use the user's role to authorize requests.
This implementation uses JSR 250 SecurityContext and security annotations.
