Add Retry plugin to http client

[dominikb]

Hi 👋

This addresses Issue #5 but two things are left to do:

• Test that the Retry plugin can be disabled (Can you point me in the right direction on how I would go about this?)
• Allow configuration of the plugin by passing an options array to it. Should this also be configurable in FreshBooksClientConfig? Maybe via a simple array?

Also, I'm trying to contribute to Hacktoberfest. Could you label the issue with hacktoberfest?

[amcintosh]

Hi!
Thanks for the PR! I have added the label.

Thinking about it again:

• Testing would be difficult as you would need to somehow get a 5xx error out of the API. Also, this is basically testing if the retry plugin works, which really is something the plugin maintainers handle, so I think we can skip that.
• Looking at the plugin, I think it's fine to have a simple enable/disable right now with the autoRetry config option you linked it to. The only thing I'm thinking to change is the number of retries. I like a default of 3, but I'd be open to that being something that can be changed.

[dominikb]

Thanks for the response.

I've added an additional paramter to customize the number of retries. I've decided against validating the range of $retries because the retry plugin can handle 0 and negative values.

[amcintosh]

Thank you for this!