Json Validation does not accept "null" as valid json

[saadkalim-earnin]

Describe the issue
When the json "null" is sent in the request body, an exception is thrown in org.mockserver.matchers.JsonStringMatcher#matches
org.json.JSONException: Unparsable JSON string: null.

This means I am unable to match an expectation when the body is the json "null".

I think the problem is in the JSONAssert library
skyscreamer/JSONassert#83

What you are trying to do
Set up an expectation in mock server with "null" as the body, content type json.
Try to match this expectation by making a request to mock server with "null" as the body. The content type should be json.

MockServer version
5.9.1-SNAPSHOT

To Reproduce
Steps to reproduce the issue:

1. Set up an expectation in mock server with "null" as the body, content type json.
2. Try to match this expectation by making a request to mock server with "null" as the body. The content type should be json.
   org.json.JSONException: Unparsable JSON string: null at org.mockserver.matchers.JsonStringMatcher#matches

Expected behaviour
"null" should be allowed as valid json, as discussed here https://stackoverflow.com/questions/8526995/is-null-valid-json-4-bytes-nothing-else.

MockServer Log

2020-02-19 11:45:09  org.mockserver.log.MockServerEventLog  FINE  failed to perform json match

	null

 with

	null

 because

	Unparsable JSON string: null

[jamesdbloom]

This has now been fixed as I have replaced JSONassert with JsonUnit as per #738

[JavierSegoviaCordoba]

@jamesdbloom is it possible to disable Json validation?