p2-inc/keycloak-magic-link ? reverse-engineered prompt

Build me a Keycloak login extension that lets people sign in with a magic link sent to their email, so they can start on one device and finish on another without needing a password. I want it to work as a normal login option in the browser flow, and if the email does not match an existing account, it can create the user and optionally send them through profile or password setup.

Please also include the continuation step for the magic link flow, plus a simple email OTP option. Make the email message easy to customize with a theme template, and keep it set up so another Keycloak project can use it as a library and extend the behavior through the SPI if needed. If there are any current Keycloak or build requirements I should know about, look them up online and use the right approach.