Expand environment variables in the learning transport connection string

[ramonsmits]

This make it possible to do for example %TEMP%\.learningTransport

[danielmarbach]

This will only properly work if you do it also for LearningTransportCustomization connection strings where we set the storage directory. Pushed an update

[danielmarbach]

I actually think this would be a great feature enhancement to Core @ramonsmits Maybe send in a to the core learning transport?

[ramonsmits]

@danielmarbach I considered that first but as learning transport is initialized via code in core and not via a connection string (I think..) adding ENVVAR expanding is up to the developer.