* implement correct Etag and If-None-Match handling, responding with
304 Not Modified if they match
* introduce SessionState and State string type aliases to ensure we are
using the correct fields for those, respectively
* extract the SessionState from the JMAP response bodies in the
groupware framework instead of having to do that in every single
groupware API
* use uint instead of int in some places to clarify that the values are
>= 0
* trace-log how long a Session was held in cache before being evicted
* add Trace-Id header handling: add to response when specified in
request, and implement a custom request logger to include it as a
field
* implement a more compact trace-logging of all the methods and URIs
that are served, to put them into a single log entry instead of
creating one log entry for every URI
* after having decided that the Groupware API should be a standalone
independent custom REST API that is using JMAP data models as much as
possible,
* removed Groupware APIs from the Graph service
* moved Groupware implementation to the Groupware service, and
refactored a few things accordingly
