* 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
* the "position" attribute is always set to 0 when using an anchor for
pagination, but it does not accurately reflect the position and thus
we decided to remove the attribute from the resulting object for
clarity
* omit "canCalculateChanges" attribute when its value is "true", which
is going to be the case in 100% of calls against Stalwart
* JMAP query limit of 0 is synonymous with "no limit", but we actually
want to be able to perform queries without any results, for cases
where we only want to count the total number of objects, and also
because it makes more sense semantically
* introduce query parameter validation checks, in order to only allow
query parameters that are actually supported, which is going to be
useful during development of clients
* adds creating addressbooks, calendars, mailboxes
* adds deleting mailbox, event, identity
* adds modifying an email
* introduce template functions for the Groupware API in templates.go,
and use those in route function implementations whenever possible
* add capability checking for mail, quota, blobs
* adds Changes interface
* adds JmapResponse interface
* jmap: add UpdateContactCard and UpdateCalendarEvent funcs
* use JSON marshalling and unmarshalling into a map for toPatch()
implementations
* add updating ContactCards and CalendarEvents to tests
* add deleting ContactCards and CalendarEvents to tests
* make query response totals work when the value is 0
* tests: use CreateContactCard and CreateCalendarEvent funcs to create
objects in tests instead of using a different JMAP stack that works
with untyped maps
* 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
