[cpp rest-sdk] Response headers handler

[whoan]

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Description of the PR

Support processing the HTTP response headers through a handler that can be set in the ApiClient class.

Some APIs (like this) return useful information in the response headers, so this PR is to support processing them.

Ping @ravinikam @stkrwork @fvarose @etherealjoy @MartinDelille

[etherealjoy]

What about error status? no need for headers there?

[whoan]

@etherealjoy If I understand your question(s), with the status code is not enough to get all the information some APIs send. As an example, the one I am using send information about remaining requests in the headers.

[etherealjoy]

@whoan
It looks OK, but did you compile the sample code?

@etherealjoy If I understand your question(s), with the status code is not enough to get all the information some APIs send. As an example, the one I am using send information about remaining requests in the headers.

What I meant here if you want to invoke header handler callback when a 400 is received for example.

[whoan]

@ethanjcohen Yes, I compiled the code. Before the last commit I hadn't done, but now I did and it is working fine.

Regarding the status code, changing the handler signature to receive it would be a good improvement indeed. Do you want me to do it in this PR?

[etherealjoy]

@whoan
You can do it later.

[wing328]

@whoan thanks for the PR, which has been included in the v3.3.4 release: https://twitter.com/oas_generator/status/1068772409795207168