Adding Member (POST)

Endpoint: POST /api/users.php

Adds an existing user account to the club (requires write permissions and admin role).

Body: username (required), role (admin / dispatcher / pilot, defaults to pilot).

On Basic tier: rejected with 403 once the club already has 3 active (non-inactive) members, and role is always forced to dispatcher regardless of what was requested - Basic tier has no admin/pilot distinction among invited members.