Enhancements for Spring Boot Admin registration

[bart-vmware]

Description

This PR enhances the registration process of Steeltoe apps with a Spring Boot Admin server.

• Periodically re-register (on by default), for resiliency against SBA server restarts
• New settings to override the app scheme/host/port/path to register with (for running behind a reverse proxy)
• Respond to configuration changes at runtime (unregister from previous server if URL changed)
• Improved logging of the registration process, improved test coverage
• Use the full Steeltoe version in the User-Agent header of outbound HTTP requests
• Enhanced detection of app URL for Spring Boot Admin
  • Take the settings for exposing management endpoints on an alternate port into account
  • Use detection logic for local host/IP similar to Eureka
  • Infer the scheme and port (not the hostname, if wildcard) from ASP.NET address bindings, prefer https if multiple
  • Works with ASP.NET dynamic port bindings

Breaking changes:

• BasePath configuration key was renamed to BaseUrl (new key BasePath means something else)
• Default value for ConnectionTimeoutMs setting reduced to 5 seconds

Fixes #490

Quality checklist

• Your code complies with our Coding Style.
• You've updated unit and/or integration tests for your change, where applicable.
• You've updated documentation for your change, where applicable.
  Documentation PR: Update documentation for Spring Boot Admin registration Documentation#371
  Samples PR: Update sample for Spring Boot Admin registration Samples#387
• There's an open issue for the PR that you are making. If you'd like to propose a new feature or change, please open an issue to discuss the change or find an existing issue.
• You've added required license files and/or file headers (explaining where the code came from with proper attribution), where code is copied from StackOverflow, a blog, or OSS.

[bart-vmware]

The Config Server flaky test fix is based on the following log fragment:

Steeltoe.Configuration.ConfigServer.Test.ConfigServerConfigurationProviderTest.Load_ConfigServerReturnsBadStatus_FailFastEnabled_RetryEnabled

Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(Steeltoe.Configuration.ConfigServer.ConfigServerException)
Actual:   typeof(System.Threading.Tasks.TaskCanceledException)


Captured logs:
DBUG Steeltoe.Configuration.ConfigServer.ConfigServerConfigurationProvider: Fetching configuration from server at: http://localhost:8888/
TRCE Steeltoe.Configuration.ConfigServer.ConfigServerConfigurationProvider: Processing label ''
TRCE Steeltoe.Configuration.ConfigServer.ConfigServerConfigurationProvider: Entered RemoteLoadAsync
TRCE Steeltoe.Configuration.ConfigServer.ConfigServerConfigurationProvider: Building HTTP request message
TRCE Steeltoe.Configuration.ConfigServer.ConfigServerConfigurationProvider: Sending HTTP request


---- Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(Steeltoe.Configuration.ConfigServer.ConfigServerException)
Actual:   typeof(System.Threading.Tasks.TaskCanceledException)
-------- System.Threading.Tasks.TaskCanceledException : The operation was canceled.
------------ System.Net.Http.HttpRequestException : Error while copying content to a stream.
---------------- System.IO.IOException :
-------------------- System.IO.IOException : The client aborted the request.

The new diagnostics are starting to prove helpful. A 10 ms timeout is way too short, so I changed it to 1 sec. The other test is supposed to trigger a timeout, so it can be shortened.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[TimHess]

LGTM!