feat: Add NetworkError to distinguish between network and API errors

[Copilot]

Previously, all Faraday network errors (DNS failures, connection timeouts, SSL errors) were re-raised as generic Twilio::REST::TwilioError, making it impossible for consumers to distinguish between retryable network errors and non-retryable API errors.

This change introduces a new Twilio::REST::NetworkError class that inherits from TwilioError and is raised specifically for network-level failures. This allows consumers to implement intelligent retry logic:

begin
  client.messages.create(to: "+1234567890", from: "+0987654321", body: "Hello!")
rescue Twilio::REST::NetworkError => e
  # Retry network errors (DNS failures, timeouts, connection issues)
  retry_with_exponential_backoff
rescue Twilio::REST::RestError => e  
  # Don't retry API errors (401, 400, 403, etc.)
  handle_api_error(e)
end

Changes Made

• Added NetworkError class in lib/twilio-ruby/framework/rest/error.rb
• Updated HTTP client in lib/twilio-ruby/http/http_client.rb to raise NetworkError for Faraday::Error exceptions
• Updated tests to verify the new error distinction functionality

Error Classification

• NetworkError (should retry): DNS resolution failures, connection timeouts, network unreachable
• RestError (should not retry): HTTP 4xx/5xx responses from Twilio API
• TwilioError (base class): Both inherit from this for full backward compatibility

Backward Compatibility

Fully maintained - existing code catching TwilioError continues to work unchanged since NetworkError inherits from TwilioError.

Fixes #689.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[github-advanced-security]

CodeQL found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud