Supporting gzipped data transfer between client and server

[anchita-g]

• Evaluate if all the components (Android FHIR SDK - FHIR Engine, Information Gateway) involved in the example for E2E sync in this repo support gzip encoding of data for transfer with the server.
• Run a sample case of sync to validate the E2E sync's correctness.
• It would be good to have some performance metrics to compare the effect of compressing the data for transfer on the entire sync time of resources.

[anchita-g]

Update:
Android FHIR SDK uses OkHttp client which performs transparent gzip. It sends the required Accept-Encoding header with value gzip by default unless asked otherwise. If the server supports the encoding, it can response back with the respective header i.e. Content-Encoding = gzip. So there is no explicit support that is required to support gzip in Android FHIR SDK.

[anchita-g]

Update:
As for FHIR Information Gateway, it does not allow relaying the Accept-Encoding header to the FHIR resource server. I have filed an issue to support gzip as an encoding.