* remove the baseurl from the JMAP client configuration, and pass it to
the session retrieval functions instead, as that is really the only
place where it is relevant, and we gain flexibility to discover that
session URL differently in the future without having to touch the
JMAP client
* move the default account identifier handling from the JMAP package to
the Groupware one, as it really has nothing to do with JMAP itself,
and is an opinionated feature of the Groupware REST API instead
* add an event listener interface for JMAP events to be more flexible
and universal, typically for metrics that are defined on the API
level that uses the JMAP client
* add errors for when default accounts cannot be determined
* split groupware_framework.go into groupware_framework.go,
groupware_request.go and groupware_response.go
* move the accountId logging into the Groupware level instead of JMAP
since it can also be relevant to other operations that might be
worthy of logging before the JMAP client is even invoked