Partial Startup

Startup.cs

app.UseOrchardCore(a => a.Run(async context =>
{
    // ShellSettings provide the tenant's configuration.
    var shellSettings = context.RequestServices.GetRequiredService<ShellSettings>();
    
    // Read the tenant-specific custom setting.
    var customSetting = shellSettings.Configuration["CustomSetting"];

    // Resolve all registered IMessageProvider services.
    var messageProviders = context.RequestServices.GetServices<IMessageProvider>();

    // Invoke all IMessageProviders.
    var messages = (await Task.WhenAll(messageProviders.Select(async x => await x.GetMessageAsync()))).ToList();

    // Add the custom setting as a message. Alternatively, could have implemented another IMessageProvider that reads the
    messages.Insert(0, customSetting);

    // Concatenate all messages.
    var output = string.Join("\r\n", messages);

    // Write the output string to the response stream.
    await context.Response.WriteAsync(output);
}));