[BUG][Java] Incompatibility between typeMapping and supportUrlQuery

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

When using type mapping for some model objects to Map with native library, the generator produces a class that doesn't compile because the type mapping is not taken into account in the toUrlQueryString() method. While the attribute type has been correctly changed following the type mapping, the implementation of toUrlQueryString() doesn't take the change into account calling an non-existent method.

The problem happens by default with native library (because supportUrlQuery is set to true by default for this library), but if you explicitly set supportUrlQuery to false, the result builds (because there's no toUrlQueryString() method).

The problem happens also for other libraries if you explicitly set supportUrlQuery to true.

    private Map fields;
...
    public Map getFields() {
        return fields;
    }
....
    if (getFields() != null) {
        joiner.add(getFields().toUrlQueryString(prefix + "fields" + suffix)); // <= DOESN'T COMPILE
    }
....

openapi-generator version

I saw the problem with version 6.6.0, but I reproduced the problem with master : see the sample and test reproducing the problem

OpenAPI declaration file content or url

Simple OpenAPI declaration file used by the test reproducing the problem

Generation Details

See test reproducing the problem.

Steps to reproduce

See test reproducing the problem.

The generated model file shouldn't call getFields().toUrlQueryString().

Related issues/PRs

Suggest a fix

The problem seems to happen because pojo.mustache relies on {{#isModel}} to decide if it can use a call to toUrlQueryString() instead of a manual encoding (Java/pojo.mustache, Java/libraries/native/pojo.mustache) but {{#isModel}} doesn't take into account the type mapping.

Start with the linked reproducing test and compare the Java template files at modules/openapi-generator/src/main/resources/Java/pojo.mustache and Java/libraries/native/pojo.mustache, focusing on their isModel handling. Regenerate the sample model with typeMapping and supportUrlQuery enabled; done means the generated model no longer calls toUrlQueryString() on a mapped Map and compiles.