Simplify error parsing

[garrytrue]

I think HttpException.extractFromHttpException can return NetworkResponse.ServerError instead if NetworkResponse.

And one more, you have broken test in ErrorExtractionTest

If you allow me I can make a PR with fixes

[haroldadmin]

Thank you for pointing out the issue. I looked into the testing setup as a result and as it turns out, most of the tests are not being picked up by Gradle.

The project right now has 42 tests, but running ./gradlew clean test only executes 18 of them. This is why I missed the broken test in ErrorExtractionTest. I have found there are a few other broken tests too which need fixing.

The reason is that some test classes do not extend from a base class of kotlintest library. I am working on a fix for this.

Regarding the HttpException.extractFromHttpException point, I think you're right. An HTTP exception by definition indicates that an error response was received from the server, so classifying it as something other than a ServerError would be silly.

Feel free to make a PR for this, I am happy to accept external contributions.

[haroldadmin]

Closed with #11