Email Verification

[libkush]

1. Every registration creates a user whose email is not verified by default.
2. After registration, create a signed JWT with exp set to 5 minutes. Send a link https://<api-url>/verify/{jwt} via an SMTP service where jwt is the one just created.
3. Listen for GET requests at endpoint /verify/{jwt}, set verified = true for the userId encoded in the JWT once the JWT is verified.

[TheChilledBuffalo]

@libkush If you haven't started working on this, can I do it?