Local dev support for property sets

[alex-wiggle]

Hi there!,

I'm attempting local development using the apigee setup described in the docs (VS code, docker etc) but I can't seem to get any property sets to work in target endpoint definitions. 

For example: I have a property set called `system.properties` with a key value such as: 

endpoints.ct.path=somepath 

If I try to refer to this property in my targets:

<TargetEndpoint name="default">
    <HTTPTargetConnection>
        <LoadBalancer>
            <Server name="server0"/>
        </LoadBalancer>
        <Path>/{propertyset.system.endpoints.ct.path}</Path>
    </HTTPTargetConnection>
</TargetEndpoint>

All calls that I make result in:

{"fault":{"faultstring":"Illegal propertyset keysystem.endpoints.ct.path","detail":{"errorcode":"Bad Request"}}}

I have tried all manner of combinations to get this to work (e.g. propertyset.system.properties.endpoints.ct.path, propertyset.endpoints.ct.path) but to no avail. 

What I'm trying to achieve is a per-env deployment configuration (different servers managed via targets but different paths via propertysets).

Has anyone come across a solution or know how to debug this?

Cheers!