Standardized diagnostics for any ASP.NET Core app

Imagine if you could go to /_diagnostics for any ASP.NET Core app and you see a list of the common things that might be issues for customers
If- you're using routing, you see the routes
- In EF, you see that your DB isn't up to date with the latest migration
- You're given an option to run the migration
- SignalR
- You have a hub but you don't have the hub wired up in the endpoint list
- Configuration
- A page you could go to that would show you all of the configuration providers and what's configured in each of the providers
- We added a feature called IConfigurationRoot.Print (he thinks, something like this) that would show you all of the configuration sources and which value came from which source

- Ability to see everything related to Authz in one place

Related: https://github.com/aspnet/specs/pull/526/files?short_path=385ad1d#diff-385ad1d05710ca57612c61303ce52e6cd94e301021bc0501e6d24a653d430004