The package has been updated to 0.4 which will result in an auto-migration of the config. This updates our config to match the new expected format. Assertions have been added to warn users that they need to migrate their configuration.
enabledInstances is an attrset: the previous logic would always pass and
result in, for example, a `mautrix-meta` and a
`mautrix-meta-registration` group being shipped to every nixos machine
whether mautrix was enabled or not.
