Other: Handle Seen/Flagged IMAP flags when APPENDing a message

When an IMAP client appends a message to a mailbox, it can specify
which flags it wants the appended message to have. We need to handle
these in a proton-specific way; not-seen messages need to be imported
with the Unread bool set to true, and flagged messages need to
additionally be imported with the Starred label.

pkg/message/build.go

@@ -234,7 +234,7 @@ func buildPGPRFC822(kr *crypto.KeyRing, msg liteapi.Message, opts JobOptions) ([
 
 	hdr := getMessageHeader(msg, opts)
 
-	sigs, err := msg.ExtractSignatures(kr)
+	sigs, err := liteapi.ExtractSignatures(kr, msg.Body)
 	if err != nil {
 		log.WithError(err).WithField("id", msg.ID).Warn("Extract signature failed")
 	}

pkg/mime/encoding.go

@@ -25,13 +25,22 @@ import (
 	"strings"
 	"unicode/utf8"
 
+	"github.com/ProtonMail/gluon/rfc822"
+	"github.com/emersion/go-message"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"gitlab.protontech.ch/go/liteapi"
 	"golang.org/x/net/html/charset"
 	"golang.org/x/text/encoding"
 	"golang.org/x/text/encoding/htmlindex"
 )
 
+func init() {
+	rfc822.ParseMediaType = ParseMediaType
+	liteapi.CharsetReader = CharsetReader
+	message.CharsetReader = CharsetReader
+}
+
 func CharsetReader(charset string, input io.Reader) (io.Reader, error) {
 	dec, err := SelectDecoder(charset)
 	if err != nil {