matrixsynapse: Enabling public registrations causes the server to stop running
This is due to configuration change: https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#enable_registration
https://discuss.freedombox.org/t/matrix-wont-start-with-public-registration-enabled/2185
https://ems-docs.element.io/books/element-cloud-documentation/page/token-based-registration