Sample demonstrating dependency injection in Azure Functions V2.
It's based on how ILogger is injected into the default function signature.
By using IWebJobsStartup we get access to the IServiceCollection instance where we register our IWelcomeService.
By following how Host binds function parameters as per https://github.com/Azure/azure-webjobs-sdk-extensions/wiki/The-Binding-Process we register IBindingProvider to our GenericBindingProvider which does the whole job.