Dynamic Access-Control-Expose-Headers Support

[yinheli]

Add Dynamic Support for Access-Control-Expose-Headers

This PR implements dynamic support for the Access-Control-Expose-Headers header in php-cors, addressing the need for more flexible CORS header management in complex applications.

Proposal issue: #29

Changes

• Update CorsService to merge existing exposed headers with configured
• Add deduplication for exposed headers

Benefits

• Allows developers to set exposed headers dynamically at the controller or middleware level.
• Provides greater flexibility for applications with diverse API endpoints requiring different header exposures.
• Maintains backwards compatibility with existing global configuration.

Testing

I've added new unit tests to cover.

Feedback and suggestions are welcome. Thank you!