FerroEHR's public sandbox now opens on the admin console

I will be transitioning to use the FerroEHR Rust crates inside anarchie - it makes sense not to duplicate the effort of writing and maintaining ‘openEHR Rust SDK’ if we are all using the same stuff. If I find any bugs or missing features during the port I’ll raise an Issue or send a PR. I’ll continue developing anarchie - even though to some extent FerroEHR is a far better option for orthodox use-cases.