Groupware improvements

* 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

pkg/structs/structs.go

@@ -1,6 +1,10 @@
 // Package structs provides some utility functions for dealing with structs.
 package structs
 
+import (
+	orderedmap "github.com/wk8/go-ordered-map"
+)
+
 // CopyOrZeroValue returns a copy of s if s is not nil otherwise the zero value of T will be returned.
 func CopyOrZeroValue[T any](s *T) *T {
 	cp := new(T)
@@ -9,3 +13,20 @@ func CopyOrZeroValue[T any](s *T) *T {
 	}
 	return cp
 }
+
+// Returns a copy of an array with a unique set of elements.
+//
+// Element order is retained.
+func Uniq[T comparable](source []T) []T {
+	m := orderedmap.New()
+	for _, v := range source {
+		m.Set(v, true)
+	}
+	set := make([]T, m.Len())
+	i := 0
+	for pair := m.Oldest(); pair != nil; pair = pair.Next() {
+		set[i] = pair.Key.(T)
+		i++
+	}
+	return set
+}