public static EndpointBuilder MapHello(this EndpointDataSourceBuilder builder, string template, string greeter)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            var pipeline = builder.CreateApplicationBuilder()
                           .UseHello(greeter)
                           .Build();

            return(builder.MapEndpoint(
                       pipeline,
                       template,
                       "Hello"));
        }