feat: reusable odata

[NicoleMGomes]

Disclaimer: Do not include SAP-internal or customer-specific information in this PR (e.g. internal system URLs, customer names, tenant IDs, or confidential configurations). This is a public repository.

Description

Introduces a new sap_cloud_sdk.core.odata module that provides reusable, destination-aware OData v4 abstractions for the SAP Cloud SDK for Python. This PoC lays the foundation for typed, fluent OData clients without requiring code generation at runtime.

Key additions:

• ODataHttpTransport — synchronous HTTP transport (requests-based) with automatic CSRF token fetching, retry on 403, and status-code–to-exception mapping.
• AsyncODataHttpTransport — async mirror using httpx.AsyncClient, usable as an async context manager with concurrency-safe CSRF token caching.
• odata_transport_from_destination — factory that wires a resolved BTP Destination into an ODataHttpTransport, inheriting its auth tokens and ERP headers.
• ODataEntity — base dataclass for typed entity models (_entity_set, _key_fields, to_dict(), key_dict()).
• Request builders — generic fluent CRUD builders: GetAllRequestBuilder, GetByKeyRequestBuilder, CreateRequestBuilder, UpdateRequestBuilder, DeleteRequestBuilder.
• StructuredQuery — immutable OData v4 query parameter builder ($select, $filter, $orderby, $top, $skip, $expand, custom params).
• FilterExpression — composable $filter DSL with field comparisons (eq, ne, lt, le, gt, ge, contains, startswith, endswith) and logical combinators (and_, or_, not_).
• ODataPageIterator — server-driven pagination following @odata.nextLink.
• CsrfTokenProvider — synchronous CSRF token provider with lazy fetch and invalidation.
• Exception hierarchy — ODataError, ODataRequestError, ODataNotFoundError, ODataAuthError, ODataDeserializationError, ODataCsrfError.
• Module.ODATA telemetry enum value added.
• Two design proposal documents in docs/proposals/.
• Unit test suite covering all components.

Related Issue

Closes #

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Dependency update

How to Test

1. Install the package: uv sync
2. Run the OData unit tests:

   uv run pytest tests/core/unit/odata/ -v
   

3. To exercise the transport manually, construct an ODataHttpTransport with a requests.Session pointing at any OData v4 service and call GetAllRequestBuilder(transport, MyEntity).top(5).execute().
4. To test the destination integration, resolve a BTP HTTP destination and call odata_transport_from_destination(destination).
5. Verify all existing tests still pass: uv run pytest

Checklist

• I have read the Contributing Guidelines
• I have verified that my changes solve the issue
• I have added/updated automated tests to cover my changes
• All tests pass locally
• I have verified that my code follows the Code Guidelines
• I have updated documentation (if applicable)
• I have added type hints for all public APIs
• My code does not contain sensitive information (credentials, tokens, etc.)
• I have followed Conventional Commits for commit messages

Additional Notes

This is a PoC / foundational PR. The public API surface (especially request builders and entity base class) is intentionally minimal and may evolve based on feedback before a stable release. The docs/proposals/ documents capture the longer-term vision for code generation and client abstractions.