Add bearer token authentication to HyperSync client

[JasoonS]

Summary

This PR implements required bearer token authentication for the HyperSync client. All HTTP requests to the HyperSync server now include an Authorization: Bearer <token> header, and client creation fails if no token is provided.

Key Changes

• Authentication enforcement: Modified BearerToken field in options.Node from optional pointer to required string
• Validation: Added Validate() method to Node struct that checks for required BearerToken and Endpoint fields
• Client initialization: Updated NewClient() to validate options before creating a client, returning an error if validation fails
• Header management: Introduced setHeaders() method in Client to consistently apply Content-Type and Authorization headers across all HTTP requests (DoQuery, Do, and DoArrow functions)
• Documentation: Added authentication section to README with configuration example and usage instructions
• Test coverage: Added comprehensive test suite (client_auth_test.go) covering:
  • Bearer token requirement validation
  • Endpoint requirement validation
  • Bearer token transmission on requests
  • Options validation for both valid and invalid configurations
• Examples: Updated all example files to read bearer token from HYPERSYNC_BEARER_TOKEN environment variable
• Test fixtures: Updated existing tests to include BearerToken in test configurations

Implementation Details

• The bearer token is now sent as Authorization: Bearer <token> on all HTTP requests to the HyperSync API
• Validation occurs at client creation time, providing early feedback for missing credentials
• The setHeaders() method centralizes header management, ensuring consistency across different request types
• All examples demonstrate the recommended pattern of reading the token from environment variables

https://claude.ai/code/session_018BC1bRoMssshsxRzNm2Knd