When there are multiple active IDO instances on the same node, before this
commit, all of them would share a single DbValue object for the notification_id
column of the icinga_contactnotifications table. This resulted in the issue
that one database references the notification_id in another database.
This commit fixes this by using a separate DbValue value for each IDO instance.
This needs a new signal as the existing OnQuery and OnMultipleQueries signals
perform the same queries on all IDO instances, but different queries are needed
here per instance (they only differ in the referenced DbValue). Therefore, a
new signal OnMakeQueries is added that takes a std::function which is called
once per IDO instance and can access callbacks to perform one or multiple
queries only on this specific IDO instance.