ConfigServerClientOptions-related Enhancements

[TimHess]

IHostApplicationBuilder.AddConfigServer should have an overload that takes a ConfigServerClientOptions instance.

Furthermore, the following code in Steeltoe:

if (!string.IsNullOrEmpty(hostEnvironment.EnvironmentName) &&
    hostEnvironment.EnvironmentName != "Production")
{
    // Only take IHostEnvironment.EnvironmentName when it was explicitly set (it defaults to "Production").
    // In the default case, we want the various other ways of setting the environment name to kick in.
    options.Environment = hostEnvironment.EnvironmentName;
}

is problematic. ConfigServerClientOptions.EnvironmentName should default to an empty string, and then ConfigServerConfigurationProvider should assume Production if still empty.

[bart-vmware]

Actually, it would be better to take an Action<ConfigServerClientOptions> that is passed into ConfigServerConfigurationProvider, so it can re-execute the delegate each time configuration is reloaded.

[bart-vmware]

Fixed in #1667.