feat: implement auditlog ng client

[simeongelovski]

Summary

This PR introduces a new auditlog_ng client for the SAP Cloud SDK for Python.

The new client enables sending Audit Log Service NG (v3) events over OTLP/gRPC and is designed for integration into Python services and agents.

What’s included

• New sap_cloud_sdk.core.auditlog_ng module
• AuditClient + create_client() factory
• Generated protobuf support for Audit Log event schemas
• Event validation via protovalidate
• Telemetry integration for client creation
• Unit tests, proto generation flow, and packaging support

Usage

Example:

from sap_cloud_sdk.core.auditlog_ng import create_client
from sap_cloud_sdk.core.auditlog_ng.gen.sap.auditlog.auditevent.v2 import auditevent_pb2 as pb

client = create_client(
    endpoint="localhost:4317",
    deployment_id="my-deployment",
    namespace="sap.als",
    insecure=True,
)

event = pb.DataAccess()
event_id = client.send(event, "DataAccess")
client.close()

Testing

Added unit tests under tests/core/unit/auditlog_ng

[cla-assistant]

All committers have signed the CLA.

[jeanscherf]

The gen/ directory contains generated *_pb2.py files but there are no .proto source files checked in. Without the sources no one can regenerate or update the generated code.

• Add proto source files to src/sap_cloud_sdk/core/auditlog_ng/proto/ with a
  buf.yaml and buf.gen.yaml that configure output into gen/ and src/buf/.
  (really liked buf btw! Thanks for the suggestion!).

• Also add a Makefile at the repo root with at minimum:

.PHONY: proto
proto:
    cd src/sap_cloud_sdk/core/auditlog_ng/proto && buf generate

• Add .github/workflows/proto-verify.yml that runs
  make proto and then git diff --exit-code to fail the PR if generated files differ.

Let me know if you need any help with all that.

[jeanscherf]

Great work! Thank you for the contribution!
LGTM