https://matrix-org.github.io/synapse/latest/setup/installation.html
https://matrix.org/docs/develop/
https://www.howtoforge.com/tutorial/how-to-install-matrix-synapse-on-ubuntu-1804/
https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#enable_registration_captcha
https://adfinis.com/en/blog/how-to-set-up-your-own-matrix-org-homeserver-with-federation/