Support orientation in RetrieveTranscription & ListTranscirptions

Depends #850 (closed)

The serializer for RetrieveTranscription & ListTranscriptions must expose the text orientation.

added 1 deleted label

mentioned in issue frontend#793 (closed)

mentioned in merge request !1502 (closed)

mentioned in merge request !1520 (closed)

assigned to @mlbonhomme

closed