Add support for private "request and wait for reply"

[joerg.hampel]

When the DQMH Consortium introduced the support for private requests with DQMH 7.0, a conscious decision was made not to support synchronous requests with reply, to avoid dead-lock scenarios.

With the way we at HSE start additional DQMH modules from any given DQMH module (by sending a request from the MHL to the EHL to start and register for modules, then reply back to the calling MHL case, so the whole process becomes synchronous), it would be super helpful if we could script those private "start submodule" requests the exact same way as all other private requests.

TL;DR: Add support for private Request and Wait for Reply.

Edit: After internal discussion, let me add that I know how to make a regular request a private one by setting the access scope. I don’t want to do that - I want the private Request with Reply to be the same as all other private events, and not a modified public request.

Edit2: If you scroll down, you'll see that Manu added a vital piece of information. We usually communicate with one of the EHLs/Helper Loops, not the MHL. So scripting should not create another case in the MHL but keep the reply in the targeted EHL/Helper Loop.

[ManuelSebald]

I like this idea, but this private Request with Replay should be a bit different to the normal ones. It should not create a new case in the MHL, it should only create a new event structure case in the EHL which was selected in the wizzard (like the option for private Requests to select the EHL) and add the "Send Notification" node there.

In other words: The private Request with Reply should be a pure module internal MHL to EHL (and helper loops) communication.

This way we prevent the danger of deadlocks in the MHL.