[C++] [Qt5] Add request compression and handling identity

[etherealjoy]

Summay
Support request compression and improve response compression support in Qt5 client.

Changes

• Split response and request compression
• Add request compression
• Add handling of identity Content-Encoding
• Default gzip for requests and response compression

Sample Test spec

---
# This is a sample Swagger spec, describing a simple API as a starting point.

swagger: "2.0"
info:
  description: Application Test Description
  version: 1.0.0
  title: ApplicationTemplate

host: 0.0.0.0:8080
basePath: /api
schemes:
- http

tags:
- name : CompressionTestServices
  x-displayName : "CompressionTestServices"
  description : |
    "Test Services offered by the application"

paths:
  /simpleEndpoint:
    post:
      tags:
        - CompressionTestServices
      summary: provide a list of Notifications
      operationId: setGetCompressedData
      consumes:
        - application/json
      produces:
        - application/json
      parameters:
        - name: reqBody
          in: body
          required: true
          schema:
            $ref: '#/definitions/Message'
      responses:
        '200':
          description: Success
          schema:
            $ref: '#/definitions/Message'
        '400':
          description: Bad Request
          schema:
            $ref: '#/definitions/Message'
            
definitions:
  Message:
    description: Type to be used to inform about errors happening while executing a command.
    type: object
    properties:
      content:
        description: Provide a list of all errors happened
        type: string

Usage

#include <QCoreApplication>
#include <QObject>
#include <QtGlobal>
#include <QFile>
#include <QString>

#include "OAICompressionTestServicesApi.h"

using namespace OpenAPI;
int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    auto api = new OAICompressionTestServicesApi();
    api->setHost(QString("127.0.0.1"));
    api->setPort(8080);
    api->enableRequestCompression();
    api->enableResponseCompression();
    QFile file("request.txt");
    QByteArray bArray;
    if (file.exists()) {
        file.open(QIODevice::ReadOnly);
        bArray = file.readAll();
        file.close();
    }
    QObject::connect(api, &OAICompressionTestServicesApi::setGetCompressedDataSignalFull, [] \
(OAIHttpRequestWorker *worker, OAIMessage summary){
        Q_UNUSED(worker);
        QFile file("response.txt");
        if (file.exists()) {
            file.remove();
        }
        file.open(QIODevice::WriteOnly);
        file.write(summary.getContent().toUtf8());
        file.close();
    });
    OAIMessage msg;
    msg.setContent(QString(bArray));
    api->setGetCompressedData(msg);
    a.exec();
}

Server

• ASP.NET core with response and request compression

Verification

• Open wireshark and check the data transferred during the request and response before and after
  api->enableRequestCompression();/api->enableResponseCompression(); are called.

References

• https://zlib.net/manual.html
• https://zlib.net/zlib_how.html

@muttleyxd @ravinikam @stkrwork @MartinDelille

PR checklist

• Read the contribution guidelines.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
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[muttleyxd]

looks great!