Mismatching reads of same configuration key over same-thread request

[reborg]

During the following scenario:

• User code reads config key-1 and takes one branch in thread-1
• New config is pushed that changes key-1
• User code reads config for key-1 again in other part of code during same thread-1

Depending on the meaning for the client of key-1 the application could take one branch before and a different branch after for the same config during the same thread with potentially conflicting results.

The idea would be to make the client aware of the keys the current thread-id is accessing and at least warn about potential unwanted results.