Fix missing "extra" field in DittoProtocolAdapter#fromAdaptable.

Signed-off-by: Yufei Cai <yufei.cai@bosch.io>

protocol/src/main/java/org/eclipse/ditto/protocol/ImmutablePayload.java

@@ -219,6 +219,7 @@ static final class ImmutablePayloadBuilder implements PayloadBuilder {
         ImmutablePayloadBuilder(final Payload payload) {
             path = payload.getPath();
             value = payload.getValue().orElse(null);
+            extra = payload.getExtra().orElse(null);
             status = payload.getHttpStatus().orElse(null);
             revision = payload.getRevision().orElse(null);
             timestamp = payload.getTimestamp().orElse(null);