WIP : feat: add pause and resume subscription methods

[rahulbile]

No description provided.

[rahulbile]

@mrfelton can you please review this PR? This updates the API version to latest and adds new method to pause and resume subscription.

[aaron-junot]

Please note that there are a lot of breaking changes between API v2.7 and v2.17. Adding just these two methods will not ensure compatibility between this library and the Recurly API v2.17.

If you want to proceed with this PR, I recommend only updating the X-Api-Version to the minimum version which supports pause and resume (v2.11) while ensuring that other changes between 2.7 and 2.11 are supported.

2.10 is a version that had a lot of changes due to credit memos, so I would spend a good amount of time ensuring that Invoices aren't completely broken in the library due to these changes.

If you go that route, it might be better to break it up into several PRs to avoid having a lot of changes in a single PR.

[rahulbile]

Yes @aaron-suarez , thanks for your notes. I did observe that and doing the changes needed. We widely use the recurly API in our application, so giving it a good test. Updated the PR to be WIP.