[WIP] Updates URI Health checks to leverage IHttpClientFactory

[joncloud]

Addresses concerns in #30 by adding the Microsoft.Extensions.Http package to include lifetime management for HttpClient. This also adds functional tests for the health checks.

New Dependencies:

• Runtime: Microsoft.Extensions.Http
• Testing: https://httpbin.org

I think that we can do some work to adjust the testing dependency and change it so that we integrate directly with a testing host that mimics the same functionality, or we can host the httpbin dependency ourselves with docker.

[unaizorrilla]

Looks good, I try to merge it this weekend, thanks!

[unaizorrilla]

Hi @joncloud

Thanks for contributing with this new feature on Uri HealthChecks. I added also some code in UiAndApi sample on how to use Polly policy handlers on this Uri HealthChecks.

          var retryPolicy = HttpPolicyExtensions
                .HandleTransientHttpError()
                .Or<TimeoutRejectedException>()
                .RetryAsync(5);

            services.AddHttpClient("uri-group") //default healthcheck registration name for uri ( you can change it on AddUrlGroup )
                .AddPolicyHandler(retryPolicy);

Next time please increment the package version on dependencies.props, build is performed and when finish this create new version package 2.2.1 for this HealthChecks on Nuget.