Add health checks routing extensions

[JamesNK]

TODO:

• Support port? done later via a matcher policy Add host matcher policy to routing #5957
• Docs

Fixes #4617

[JamesNK]

@rynowak UseHealthChecks supports limiting access to a port. What do you think of shipping the DomainMatcherPolicy that I wrote as a sample in routing? Then it would be a simple matter of setting the appropriate metadata for the healthchecks endpoint.

[rynowak]

As discussed we want support for filtering on host/port, I'm ok with that to land separately.

[rynowak]

Seems good. Need to get final polish

[JamesNK]

re: host/port

UseMiddleware has port as an argument. Do you have a strong preference on whether MapHealthChecks should have an overload that takes a port and adds the metadata for you, or do we tell people to use a standard extension method to add port metadata.

I lean towards and extension method but I don't have a strong preference either way.

[rynowak]

I lean towards extension method as well if it's easy to use. If not we can add it back as first-class, so lets start with the extension method

[JamesNK]

🆙 📅