Fix flaky test testToJSONString

[219sansim]

Problem

The testToJSONString is detected flaky because the JsonHelper.toJSONString() gives a non-deterministic output as JSONObject values are unordered.

Solution

After modifying testToJSONString to expect 2 different string values, the test passes.

Reason:
The JSON object is unordered and generally uses Maps as their internal data structure. And, according to HashMap documentation,
"This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time."
This causes the JsonHelper.toJSONString() to give a non-deterministic output.

Reproduction of the error

The test fails on 5/10 runs of the NonDex tool

Command to reproduce the failure:
mvn -pl pac4j-oauth edu.illinois:nondex-maven-plugin:2.1.7-SNAPSHOT:nondex -Dtest=org.pac4j.oauth.profile.JsonHelperTests#testToJSONString -DnondexRuns=10

Error Message:

[ERROR] org.pac4j.oauth.profile.JsonHelperTests.testToJSONString -- Time elapsed: 0.396 s <<< FAILURE!
org.junit.ComparisonFailure: expected:<"{\"[id\":\"id\",\"name\":\"name]\"}"> but was:<"{\"[name\":\"name\",\"id\":\"id]\"}">

[leleuj]

Thanks for your contribution