Add support for the new Tesla version

[LeoLeiteSC]

We updated the Tesla on our project to 1.6, and apparently this operation broke the ExForce dependency. We started to receive a decode error when executing the function ExForce.OAuth.get_token/2:

Tried with the version 1.5 as well and didn't worked. Tesla 1.4 worked as expected.
Apparently the problem is with some change made in Tesla after the version 1.5.0.

[roylez]

This is because ex_force has gzip compression turned on, but when you send a accept-encoding with gzip to salesforce, the response does not contain a content-encoding header field required to trigger Tesla's Compression middleware, even though response body is indeed gzip compressed.

[jotaviobiondo]

Heyy, I work with @LeoLeiteSC and we have some updates about this issue.

The problem here is the ex_force defines the Tesla.Middleware.Compression BEFORE the JSON middleware, but it need to be defined AFTER, to follow this behavior:

• for the request, it first serializes as JSON and then compress the body
• for the response, it decompress the body and then deserializes as JSON

Currently, it's doing the inverse.