Proxy settings on aws-sdk-ios

For new projects, you should not use the AWS SDK for iOS anymore. We are focusing our efforts on a new AWS SDK for Swift (in preview).

The AWS SDK for Swift implements a custom HTTP client that bypass macOS / iOS system wide proxy settings. The solution is to provide your own HTTP Client implementation, just for the duration of your testing.

Eventually, we would like the SDK to include such client by default. You can track progress and copy/paste code sample here https://github.com/awslabs/aws-sdk-swift/issues/817