Cloned connections lacking option to have their own custom headers

[svejdo1]

Ref: https://github.com/microsoft/PowerPlatform-DataverseServiceClient/blob/master/src/GeneralTools/DataverseClient/Client/ServiceClient.cs (line 1420)

When we're cloning ServiceClient the CustomHeaders function is always set to match the parent.
This makes impossible to set custom headers per clonned connection.

[MattB-msft]

@svejdo1, thanks for your report, Yes, this is a known issue.

On the bright side, we are about to ship a new feature to address this specific issue.
This new feature is a request builder where you can set headers per request, as well as user ID, request ID and so on.

[MattB-msft]

Fixed with #444