Feat/cors: Add CORS handling to API and S3

[St4NNi]

This PR adds CORS support for browser-based access to Aruna through both the REST API and S3 interface. It also integrates bucket-level S3 CORS configuration support from feat/bucket-cors.

Changes

• Add configurable REST CORS handling.
• Add S3 CORS handling for unsigned preflight requests before signature validation.
• Add CORS headers to S3 responses so browser clients can read relevant response headers.
• Add bucket-level CORS configuration stored in BucketInfo. (This includes the changes from the branch feat/bucket_cors)
• Implement S3 PutBucketCors, GetBucketCors, and DeleteBucketCors.
• Add CORS matching/conversion helpers and focused tests.
• Include the API quick fixes needed for portal integration.

Fixed Issues

Fixes #242
Fixes #244

[das-Abroxas]

I left some comments which are not mission critical. Address these issues or just leave a comment why you don't think that this is necessary and I will approve this PR ✌️

[das-Abroxas]

Nice. There are still a few minor things that could be improved, such as using the header name constants from the http crate (e.g. http::header::ORIGIN) instead of defining them again ourselves. But, those are just design decision discussions at this point. lgtm.