Process itinerary information asynchronously

[ChristophWurst]

We currently process the itinerary information when a message is loaded for the first time. That means that we have to fetch the full body and all attachments. Depending on the network speed and processing power of the server this can slow down loading of messages quite a bit.

To improve this we could split off the kitinerary process into a separate request that is dispatched after we show the message. For fast servers that means the itinerary info will show with a very slight delay, on slow servers it can take a bit longer.