Add Junit5 extension for soft assertions

[filiphr]

Summary

Currently there is a JUnit @Rule for soft assertions. In order for JUnit5.

We can use the @RegisterWith extensions. See more here

Example

@RegisterWith
JUnitJupiterSoftAssertions softly = new JUnitJupiterSoftAssertions();

[joel-costigliola]

I wonder how having both JUnit 4 and 5 as dependencies will play out, I hope declaring them as provided would be sufficient to avoid incompatibilities (if any).

[filiphr]

There won't be any issue between the two dependencies. JUnit 5 (Jupiter) is a complete rewrite with different packages. One can even have tests with both dependencies in the same time