* add endpoints for Mailboxes:
- PATCH mailboxes/{id}
- DELETE mailboxes/{id}
- POST mailboxes
* refactor the pkg/jmap and groupware framework to systematically
return a jmap.State out-of-band of the per-method payloads, since
they are almost always present in JMAP responses, which lead to the
artificial creation of a lot of composed struct types just to also
return the State; on the downside, it adds yet another return
parameter
* the JMAP error handling was not working properly, fixed it and added
error definitions accordingly
* add operations to retrieve mailbox roles and mailboxes by role for
all accounts
* move jmap.request() to jmap.Client.request() and pass the Session
and a Logger to introduce checking the number of methodCalls within a
request not exceeding the limit of the Session, as well as error
handling and logging there instead of in each caller
* a few bugfixes:
- add a few missing Send() calls in logs
- correct the response tag matching for
GetMailboxChangesForMultipleAccounts
- fix typo in Identity.ReplyTo json serialization rune
- fix response tag in pkg/jmap/testdata/mailboxes1.json after
changing them to be prefixed by the accountId
* ensure that all the jmap responses contain the SessionState
* implement missing errors that were marked as TODO
* moved common functions from pkg/jmap and pkg/services/groupware to
pkg/log and pkg/structs to commonalize them across both source trees
* implement error handling for SetError occurences
* Email: replace anonymous map[string]bool for mailbox rights with a
MailboxRights struct, as the keys are well-defined, which allows for
properly documenting them
* introduce ObjectType as an "enum"
* fix JSON marshalling and unmarshalling of EmailBodyStructure
* move the swagger documentation structs from groupware_api.go to
groupware_docs.go
* fix: change verb for /groupware/accounts/*/vacation from POST to PUT
