This replaces all Mailman secrets with ones that are generated the
first time the service is run. This replaces the hyperkittyApiKey
option, which would lead to a secret in the world-readable store.
Even worse were the secrets hard-coded into mailman-web, which are not
just world-readable, but identical for all users!
services.mailman.hyperkittyApiKey has been removed, and so can no
longer be used to determine whether to enable Hyperkitty. In its
place, there is a new option, services.mailman.hyperkitty.enable. For
consistency, services.mailman.hyperkittyBaseUrl has been renamed to
services.mailman.hyperkitty.baseUrl.