Implement $batch OData endpoint

[kbarbounakis]

Summary

Implement the $batch OData endpoint in order to support OData batch processing requests conforming to the OData v4 specification.

Acceptance Criteria

• A new endpoint /api/$batch should be exposed.
• The endpoint must accept and process batch HTTP requests as specified by OData Protocol v4.
• Support both change sets and query operations within a batch.
• Handle atomicity groups and transactional semantics for change sets.
• Return response payload in the correct multipart/mixed OData batch format.
• Comprehensive error handling for malformed batch requests and failed operations.
• Unit and integration tests provided for different types of batch operations.

Motivation

Batch processing is essential for clients who need to perform multiple operations in a single HTTP request, optimizing both network usage and performance. Supporting $batch increases compliance with the OData v4 protocol and broadens interoperability with OData clients.

References

• OData v4.0 Part 1: Protocol, Section 11.7 Batch Requests

---

If you have any questions about batch request handling or implementation specifics, please refer to the official documentation or raise concerns in this issue.