AI-based recommendations with draft

[HeikoTheissen]

Unlike #276, in this variant the server stores the recommendations in the (collaborative) draft and updates them

• only if their input has changed (advantage, especially with collaborative draft)
• but independent of the $select clause of the client(s).

This means that recommendations are computed for all items, even if the client(s) display only the first 5 items and want recommendations only for these.

[MarcelWaechter]

Thanks, I'm fine with it. Let's see if Saurabh has any doubts

[ralfhandl]

Looks good to me, only two minor things:

• If recommendations are computed asynchronously, how long should the client wait before reading them?
• Would be nice to have a response example in recommendations.md