* in the JMAP API as well as in several places in the Groupware
framework, use a single jmap.Response[T] object to return the
payload, the language, the session state and the etag/state instead
of individual multi-valued return values
* make the JMAP internal API a bit more future-proof by passing
ObjectType objects instead of the JMAP namespaces
* remove the new attempt to contain operations even further using the
Factory objects
* move CalendarEvent operations to its own file, like everything else
* fix email tests
* ignore WS error when closing an already closed connection
* implement ContactCard retrieval endpoint for syncing
* re-implement that endpoint for Email too
* fix the Mailbox changes endpoint to actually return changes about
Mailboxes, and not about Emails
* when querying the diff of Mailboxes without any prior state, return
an error since the result is not what one would expect
* introduce the 'changes' API tag and group
* refactor the successful response functions to consistently return an
object type and object state whenever possible
* move the syncing endpoints under /accounts/*/changes/ for better
clarity, e.g. /changes/emails instead of /emails/mailbox/*/changes
* re-implement the auth-api service to authenticate Reva tokens
following the OIDC Userinfo endpoint specification
* pass the context where necessary and add an authenticator interface
to the JMAP HTTP driver, in order to select between master
authentication (which is used when GROUPWARE_JMAP_MASTER_USERNAME and
GROUPWARE_JMAP_MASTER_PASSWORD are both set) and OIDC token
forwarding through bearer auth
* add Stalwart directory configuration "idmoidc" which uses the
OpenCloud auth-api service API (/auth/) to validate the token it
received as bearer auth from the Groupware backend's JMAP client,
using it as an OIDC Userinfo endpoint
* implement optional additional shared secret to secure the Userinfo
service, as an additional path parameter
