Atrium: create maven sample project

[robstoll]

Platform (jvm, js, android): jvm
Extension (none, kotlin 1.3, jdk8): none

Code related feature

We currently provide an example-pom.xml and a settings.xml for maven.
It would be nicer if we actually have a full-working sample for maven.

Following the things you need to do:

• [x] setup a maven project in /samples/maven and include some tests -- up to you what runner you are using.
• [ ] build the sample in CI, add corresponding steps/jobs in .travis.yml and .github/workflows/java-windows.yml
• :no_entry_sign: include the new sample project in the composite build of misc/tools/atrium-samples-test => won't be possible as it is not a gradle project. That's fine though.
• [x] link to the sample project in the README -> installation -> jvm (https://github.com/robstoll/atrium#jvm) -> maven

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[robstoll]

@binkley I saw that you are using Atrium in a maven context (https://github.com/binkley/spikes/blob/master/scratch/pom.xml). Would you mind creating a sample project so that others have an easier start when using Atrium as well? (and let me know if there are things which need to be improved for maven)

[binkley]

@robstoll I'd love to! <3

What model should I follow? Any specific kinds of tests, etc.?

[robstoll]

nice :+1: the idea is to have a minimalistic setup of a maven project using Atrium and some test-runner (e.g. junit + jupiter) including a SampleTest. So that someone wanting to start out a new project and would like to use Atrium can basically copy the sample project.
You can come up with a SampleTest or copy an existing one (e.g. samples/jvm/junit5/src/test/kotlin/org/atriumlib/samples/junit5/SampleJvmTest.kt)

[binkley]

The sample looks good. The only change I'd like to make: I've run into the Kotlin convention of providing "text" test method names, ie:

fun `expect an exception occurred`() { ... }

rather than:

fun expectAnExceptionOccurred() { ... }

[robstoll]

good idea, I forgot about that for JUnit. Good with me, you can also change it in the other samples if you like.

[binkley]

PR updated to separate Gradle and Maven builds.