API: authenticate and authorize with email+password
schleuder-web und schleuder-cli should authenticate with an email-address and a password against the API.
The password should be stored with an Account, that has many subscriptions.
An account/password can be requested by keyword or button in schleuder-web. The request generates an email that contains a password (if the request was in a subscriber-signed message) or a token, which needs to be confirmed (if it was from schleuder-web).
TODO:
- Find better names, api_superadmin vs. superadmin is confusing.
Edited by paz