Use 'const' for cpp getters when returning aggregate types

Description

We are using swagger-codegen to generate C++ classes from Java. For primitive types, the C++ getter method has 'const' qualifier, but when aggregates are specified, the method does not have have the const qualifier. Can a 'const' be added for getter methods? (I am not very familiar with C++, and maybe there is a reason this is not being done. And I am filing this on behalf of someone who mentioned that not having a const on these getters causes them some grief.)

Swagger-codegen version

We are using swagger-maven-plugin v3.1.7
and swagger-generator v2.2.3

Swagger declaration file content or url

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import io.swagger.annotations.ApiModel;

import java.util.Collections;
import java.util.List;

@ApiModel
public class SampleRequest {
    private static final String MESSAGE_NAME = "messageName";
    private static final String PARAM_NAMES = "paramNames";

    @JsonProperty(MESSAGE_NAME)
    private final String messageName;

    @JsonProperty(PARAM_NAMES)
    private final List<String> paramNames;

    @JsonCreator
    public SampleRequest(
            @JsonProperty(value = MESSAGE_NAME, required = true) String messageName,
            @JsonProperty(value = PARAM_NAMES, required = true) List<String> paramNames) {
        this.messageName = messageName;
        this.paramNames = Collections.unmodifiableList(paramNames);
    }

    public String getMessageName() {
        return messageName;
    }

    public final List<String> getParamNames() {
        return paramNames;
    }
}

class  SampleRequest
    : public ModelBase
{
public:
 ...
    utility::string_t getMessageName() const; 
    std::vector<utility::string_t>& getParamNames();  // this getter doesn't have 'const'.
   
protected:
    utility::string_t m_MessageName;
    std::vector<utility::string_t> m_ParamNames;
};

Command line used for generation

Using the swagger-maven-plugin to generate the code. Please let me know if you need this.

Steps to reproduce

Please use the included sample Java code to generate a C++ class

Related issues/PRs

I looked around in the project, but did not find anything appropriate. Please let me know if I missed it.

Suggest a fix/enhancement

Use the supplied SampleRequest Java declaration to reproduce C++ generation through the swagger-maven-plugin and swagger-generator versions listed. Inspect the generated aggregate getter declaration and compare it with the primitive getter; done means aggregate getters are const-qualified while generation still succeeds for the sample.