Protected mock constructor should chain to base no-op constructor

[daviburg]

Context

The generated client classes have a protected parameterless constructor intended for mocking, but it chains to a real overload that instantiates a live ManagedIdentityCredential and builds an HTTP pipeline.

Problem

// Current — KustoClient.cs (and all generated clients)
protected KustoClient() : this(new Uri("https://localhost")) { }

This calls KustoClient(Uri) → ConnectorClientBase(Uri) → creates new ManagedIdentityCredential(ManagedIdentityId.SystemAssigned) and calls HttpPipelineBuilder.Build(...). In CI/test environments without IMDS:

• The constructor may block waiting for the metadata endpoint
• Managed identity calls can introduce latency or throw on misconfigured machines

The base class already has a no-op constructor designed for exactly this case:

// ConnectorClientBase.cs
protected ConnectorClientBase()
{
    this._pipeline = null!;
    this._connectionRuntimeUrl = string.Empty;
}

Proposed change

Chain to the base no-op constructor instead:

// Fix — safe for mocking, no live resources created
protected KustoClient() : base() { }

This is a generator template change — applies to all 90+ generated client classes.

Azure SDK guideline

DO provide a protected no-argument constructor for mocking