ServiceProvider callback for NATS DI configuration;

[william-liebert]

Issue

The NATS Client DependencyInjection package (NatsBuilder) does all configuration inline when the .AddNatsClient method is called. This does not allow consumers to build up a NATS instance across multiple packages, and all configuration must be defined at registration time, rather than runtime.

MyCompany.Nats.Core:

public static IServiceCollection AddMyCompanyNats(this IServiceCollection services)
{
    services.AddNatsClient(natsBuilder => natsBuilder
        .PoolSize(3)
        .ConfigureOptions(opts => {
            return opts; // How to configure??
         }))

    return services;
}

Proposal

Add IServiceProvider overloads to configuration methods, to enable resolution-time configuration:

MyCompany.Nats.Core:

interface IConfigurator
{
    NatsOpts Configure(NatsOpts opts);
}

public static IServiceCollection AddMyCompanyNats(this IServiceCollection services)
{
    services.AddNatsClient(natsBuilder => natsBuilder
        .PoolSize(3)
        .ConfigureOptions((serviceProvider, opts) => {
            IOptsConfigurator configurator = serviceProvider.GetRequiredService<IOptsConfigurator>();

            opts = configurator.Configure(opts);

            return opts; 
         }))

    return services;
}

MyCompany.Nats.HighSecurityCluster:

public class HighSecurityConfigurator : IConfigurator
{
    public NatsOpts Configure(NatsOpts opts) =>
        opts with {
            TlsOpts = opts.TlsOpts with {
                InsecureSkipVerify = false,
            }
        };
}

MyCompany.Nats.DemoCluster

public class DemoConfigurator : IConfigurator
{
    public NatsOpts Configure(NatsOpts opts) =>
        opts with {
            TlsOpts = opts.TlsOpts with {
                InsecureSkipVerify = true,
            }
        };
}

[mtmk]

I will fix the build in a minute ;)

edit: ok, build should work now!

[mtmk]

cc @rickdotnet

[mtmk]

thanks @william-liebert looks good 💯 I'll let @rickdotnet to have a look as well. We should be able to include this in 2.4.0.

[mtmk]

LGTM thanks @william-liebert