http-client: support returning http response without exception when status >= 400

Task List

• Steps to reproduce provided
• Stacktrace (if present) provided
• Example that reproduces the problem uploaded to Github
• Full description of the issue provided (see below)

Steps to Reproduce

1. With HttpClient, query an endpoint that returns a status code >= 400
2. Notice HttpClientResponseException is thrown

io.micronaut.http.client.exceptions.HttpClientResponseException: Conflict

	at io.micronaut.http.client.DefaultHttpClient$10.channelRead0(DefaultHttpClient.java:1821)
	at io.micronaut.http.client.DefaultHttpClient$10.channelRead0(DefaultHttpClient.java:1761)
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)

Expected Behaviour

Need HttpClient implementation that does not create nor throw an exception when full response has been received and status code >= 400. This should be a configurable option in HttpClientConfiguration.

Actual Behaviour

DefaultHttpClient always throw HttpClientResponseException when status code is >= 400. https://github.com/micronaut-projects/micronaut-core/blob/master/http-client/src/main/java/io/micronaut/http/client/DefaultHttpClient.java#L1807

Environment Information

• Operating System: Mac OS 10.14.6 (mojave)
• Micronaut Version: 1.2.3
• JDK Version: Oracle JDK 1.8.0_181

Example Application

Code identical to Mocking Collaborators official test example: https://micronaut-projects.github.io/micronaut-test/latest/guide/index.html#_mocking_collaborators but with the endpoint returning an error.

Micronaut code throwing the exception: https://github.com/micronaut-projects/micronaut-core/blob/master/http-client/src/main/java/io/micronaut/http/client/DefaultHttpClient.java#L1807

[fabienrenaud]

Is this something that could be added soon? Writing tests for error cases (code ≥ 400) using HttpClient is very cumbersome at the momen. I had to define some nasty utility methods to try/catch every call to work around this … I’d like to make micronaut mainstream on my team soon and not have to tell everyone to rewrite all their tests (to remove the utility methods) in 6 months when this ships…

[graemerocher]

I think rather than making it configurable it should be another method on the HttpClient interface