Add better message for group session withheld

bridge/crypto.go

@@ -32,6 +32,7 @@ import (
 var _ crypto.StateStore = (*sqlstatestore.SQLStateStore)(nil)
 
 var NoSessionFound = crypto.NoSessionFound
+var ErrGroupSessionWithheld = crypto.ErrGroupSessionWithheld
 var UnknownMessageIndex = olm.UnknownMessageIndex
 
 type CryptoHelper struct {

bridge/matrix.go

@@ -391,6 +391,8 @@ func errorToHumanMessage(err error) string {
 		return err.Error()
 	case errors.Is(err, UnknownMessageIndex):
 		return "the keys received by the bridge can't decrypt the message"
+	case errors.Is(err, ErrGroupSessionWithheld):
+		return "your client refused to share decryption keys with the bridge"
 	case errors.Is(err, errMessageNotEncrypted):
 		return "the message is not encrypted"
 	default:

bridge/no-crypto.go

@@ -22,4 +22,5 @@ func NewCryptoHelper(bridge *Bridge) Crypto {
 }
 
 var NoSessionFound = errors.New("nil")
+var ErrGroupSessionWithheld = NoSessionFound
 var UnknownMessageIndex = NoSessionFound