Support Async API calls

[mxr576]

Support Async API calls for loading/deleting/updating multiple entities (developers, apps, api products, etc.) from Apigee Edge much quicker.

[mxr576]

We tried to add async API calls to the API client before beta1, but we bumped into some issues by using HttpPlug's Guzzle6 and CURL Http clients. It seems the root of the problem is HttpPlug does not have its own event loop implementation and using Guzzle Promises causing troubles, because it has been built to work with Guzzle Promises and not HttpPlug promises.

We like the HTTP client agnostic idea behind HttpPlug still and just because of this problem we do not want to drop it from the API client and directly depend on Guzzle for example. We hope these problems get fixed in the upcoming releases and after that, we can add async support to our API client too.

Related issues:

• Promise\settle() is not working properly php-http/guzzle6-adapter#49
• Async requests are randomly failing php-http/curl-client#39

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.