[java][jersey2] Fix processing of additional, undeclared properties

[sebastien-rosset]

This is a fix for #6646.

1. Add more unit tests (in JSONComposedSchemaTest.java) to exercise various use cases for additionalProperties, such as:
   1. within composed schema
   2. non composed schemas
   3. additionalProperties with boolean value
   4. additionalProperties with schema
2. Fix processing of additionalProperties

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[sebastien-rosset]

@bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @bkabrda (2020/01)

[sebastien-rosset]

Historically, the behavior has been to disallow additional properties by default, but that's not compliant with the OAS spec. By default, when additionalProperties is not present, additionalProperties MUST be allowed.

@wing328 , I think at some point we should set disallowAdditionalPropertiesIfNotPresent to false by default, maybe starting with jersey2?

[wing328]

I think we should let the user choose at this point instead of forcing the behavior per generator/library.

We'll introduce this option to the community as part of the v5.0.0 official release and consider changing the default value later if more users are familiar with the change.

[sebastien-rosset]

ok, sure. This is how it is currently implemented (i.e. non-compliant). I have set disallowAdditionalPropertiesIfNotPresent to false for the example only.