Actionable error message for large json documents

[hibikiledo]

Problem

When using assertJsonDocumentMatches, it is hard to navigate the error message when the assertion fails.

The message only states that the given JSON document is not a match of the provided constraints.
It would be great to also tell which constraint(s) the JSON document fails to satisfy.

Solution

I implement additionalFailureDescription in JsonValueMatchesMany constraint to return a string representation of constraints that fail during evaluations.

The result would look like this.

I think this would greatly simplify investigation when the tests fail.

Thank you

[martin-helmich]

Thanks for the contribution, @hibikiledo! 👍 Full ACK that this is an entirely sensible change to make -- the validation messages, especially for larger assertions, are currently not optimal and can be improved significantly.

I'm just having one thought regarding the statefulness of the JsonValueMatchesAny constraint (see the respective comment). Let me know your thoughts on this.

[martin-helmich]

👍 Looking good! I just added (and already applied) one quick suggestion (whitespace only) to make codeclimate stop complaining.