[cpp][Qt5] Add the ability to pass QNetworkAccessManager as a parameter

[alfredotg]

Problem:
Every api call created new connection to server. It happens because OAIHttpRequestWorker creates new QNetworkAccessManager every time.

Solution:
Passing QNetworkAccessManager as parameter. It allows QT reusing an opened early connection if it possible (if server support keep alive connections and if there is no active request).
This change is optional and should not affect existing code.
Also I change connect to signal QNetworkReply::finished instead of QNetworkAccessManager::finished.

@ravinikam @stkrwork @etherealjoy @MartinDelille @muttleyxd

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[etherealjoy]

void {{prefix}}HttpRequestWorker::on_manager_timeout(QNetworkReply *reply)

Need to disconnect in the function from the reply

[etherealjoy]

@alfredotg
Many thanks for the PR,
I am wondering about the chance of a crash when the api object is deleted but the reply object is still alive because now it is managed by the manager and it could still call the slot.

[alfredotg]

@etherealjoy

@alfredotg
Many thanks for the PR,
I am wondering about the chance of a crash when the api object is deleted but the reply object is still alive because now it is managed by the manager and it could still call the slot.

Reply object is child of OAIHttpRequestWorker so it will be deleted with OAIHttpRequestWorker which will be deleted along with api object.

void {{prefix}}HttpRequestWorker::on_manager_timeout(QNetworkReply *reply)

Need to disconnect in the function from the *reply

Thanks. I will fix it.

[MartinDelille]

@etherealjoy I think we could improve the code memory management thanks to QSharedPointer and friends.

[alfredotg]

@etherealjoy I think we could improve the code memory management thanks to QSharedPointer and friends.

Why and where we need shared point? I thought parent-child relationships were the main way to manage memory in Qt.