Android: Allow to provide a different HttpClient implementation

[anod]

Subset of changes from #1055 to avoid pulling 3rd party library dependencies into SDK

Example of OkHttp implementation which enablex HTTP/2 support

https://github.com/microsoft/cpp_client_telemetry/blob/b6f41f6e9b974c24902b144ebf271e57ec66b2c5/lib/android_build/maesdk-okhttp/src/main/java/com/microsoft/applications/events/okhttp/OkHttpRequest.java

[anod]

@lalitb @sid-dahiya I would like to make Android HTTP client replaceable. Any concerns, suggestions?

This will allow us to use our own OkHttp implementation which supports HTTP/2 for AI integration.

[lalitb]

@anod - I am not sure how much different are APIs for OkHttp and (existing) HttpURLConnection, but do you think we can introduce HTTPClient for OkHttp as a module similar to other HTTP Clients here. So there would be two differnt HTTPClients for Android, and right one would be picked through HTTPClientFactory class as below:

#elif defined(ANRDOID AND WITH_HTTP2)
    std::shared_ptr<IHttpClient> HttpClientFactory::Create() {
        LOG_TRACE("Creating HttpClient_Android");
        return HttpClient_OkHttp_Android::GetClientInstance();
    }
#elif defined(ANDROID)
    std::shared_ptr<IHttpClient> HttpClientFactory::Create() {
        LOG_TRACE("Creating HttpClient_Android");
        return HttpClient_Android::GetClientInstance();
    }

[anod]

@anod - I am not sure how much different are APIs for OkHttp and (existing) HttpURLConnection, but do you think we can introduce HTTPClient for OkHttp as a module similar to other HTTP Clients here. So there would be two differnt HTTPClients for Android, and right one would be picked through HTTPClientFactory class as below:

#elif defined(ANRDOID AND WITH_HTTP2)
    std::shared_ptr<IHttpClient> HttpClientFactory::Create() {
        LOG_TRACE("Creating HttpClient_Android");
        return HttpClient_OkHttp_Android::GetClientInstance();
    }
#elif defined(ANDROID)
    std::shared_ptr<IHttpClient> HttpClientFactory::Create() {
        LOG_TRACE("Creating HttpClient_Android");
        return HttpClient_Android::GetClientInstance();
    }

The problem is including okhttp as dependency. This will require client app to use same or similar version of okhttp
You can see the examples in the following article

Usually libraries provide different implementations as a separate libraries, so the client can decide which implementation to use. Example from retrofit:

I can followup with adding a maesdk-okhttp module once I test it and confirm the implementation.

[lalitb]

Sorry for late reply on this. The changes look good in general if we can avoid the intermediate buffer to store the request data.
Tagging @sid-dahiya ,@mkoscumb in they want to look into these changes.

[lalitb]

@anod - Just wondering if you would like to resolve and go ahead with this PR ?

[anod]

@anod - Just wondering if you would like to resolve and go ahead with this PR ?

Yes, sorry missed the reply, I will take a look on the buffer

[lalitb]

LGTM. Thanks for the changes. We can keep for couple of days for @microsoft/1ds-c-sdk-approver to review this before merging.