Add comprehensive OData Batch operations support with examples and documentation

[Copilot]

• Implement comprehensive OData Batch functionality with examples and documentation
  • Add BatchRequestBuilder class with fluent interface for batch operations
  • Support changesets for atomic operations
  • Add batch() method to IODataClient interface and ODataClient implementation
  • Create comprehensive examples in examples/batch_operations.php
  • Add complete test coverage with BatchTest class
  • Update README with batch operations documentation
• Move guzzlehttp/guzzle back to require-dev as requested

All batch functionality is implemented and working. The library supports HTTP provider abstraction, so Guzzle is correctly placed in require-dev as an optional implementation rather than a hard requirement.

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[anderly]

@copilot move guzzle back to require-dev

[Copilot]

@copilot move guzzle back to require-dev

Done! Moved guzzlehttp/guzzle back to require-dev in commit 9e94c10. The batch functionality works through the HTTP provider abstraction, so Guzzle should be an optional dependency rather than required.