fix: avoid JSON::ParserError for all server errors

[dan-jensen]

When there is a Twilio service outage that causes the Twilio API to
return a 503 Service Unavailable error, a JSON::ParserError is
raised. This fixes that bug by detecting all 5XX server error status
codes, and handling them the same way 504 status codes were already
being handled.

This is related to the existing bug issue and is basically an expansion of a previous pull request.

Fixes #544

A short description of what this PR does.

Checklist

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• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

If you have questions, please file a support ticket, or create a GitHub Issue in this repository.

[dan-jensen]

Note: I was tempted to implement the same change for client errors by changing elsif response.status == 400 to use Faraday::Response::RaiseError::ClientErrorStatuses. But that felt like too big a change for this PR.

Also, it makes me nervous that line appears after elsif response.body && !response.body.empty?. I would think we should check for both client errors and server errors before we return the response body, so I'm a bit wary of some special intent there. But if I had to guess, I would say it was an unintentional oversight in the original implementation. I would recommend a follow-up PR to handle client errors.

[dan-jensen]

@eshanholtz would you have time to review this? Pinging you because you merged a similar PR earlier this year so I'm guessing you have the most context awareness 🙂

[doryphores]

Hello. Any movement on this? Feels like a good fix to merge in.

[childish-sambino]

LGTM