The issue reported that there was "no method to set API Key and secret" for Twilio authentication. Investigation revealed that API Key authentication already exists and works correctly in the Twilio Python SDK, but was suffering from a documentation discoverability issue.

What was already working

The Twilio Python SDK has always supported API Key authentication via:

from twilio.rest import Client

api_key = "SKXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"      # Your API Key
api_secret = "your_api_secret"                      # Your API Secret  
account_sid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"   # Your Account SID
client = Client(api_key, api_secret, account_sid)

This was documented in the README but may not have been easily discoverable.

Changes Made

1. Enhanced Documentation

• Reorganized README.md with clearer section structure and numbered authentication methods
• Made API key authentication more prominent with "Recommended for Production" label
• Added detailed parameter descriptions and format notes (e.g., API keys start with 'SK')
• Updated Client constructor docstring with clear examples for both authentication methods

2. Comprehensive Test Coverage

Added TestAuthenticationPatterns class with 5 new test methods:

• Account SID + Auth Token authentication
• API Key + Secret authentication (multiple patterns)
• Environment variable authentication
• Verification that correct authentication headers are sent in requests

3. Working Example

Created examples/api_key_authentication.py demonstrating:

• How to use API Key authentication
• Security best practices (credential masking)
• Complete working example with proper error handling

Technical Details

The API Key authentication works by:

1. Treating the API Key as the username parameter
2. Treating the API Secret as the password parameter
3. Using HTTP Basic Authentication with these credentials
4. Requiring the Account SID as a third parameter for proper account identification

All existing functionality is preserved with no breaking changes.

Fixes #3.

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