Summary

Implement gRPC transport abstraction for the OTLP metrics/traces exporter.

Parent Issue

• deps: Implement UDP and gRPC transport using common_system interfaces #273

Tasks

• Create grpc_transport.h with abstract interface
• Implement stub_grpc_transport for fallback
• Implement network_grpc_transport using common_system interfaces
• Update otlp_metrics_exporter to use gRPC transport
• Add unit tests for gRPC transport

Note

gRPC transport may require additional HTTP-based implementation as OTLP supports both gRPC and HTTP protocols. Consider implementing HTTP-based OTLP first if gRPC is too complex.

Acceptance Criteria

• gRPC/HTTP transport compiles with and without network backend
• otlp_metrics_exporter sends real requests when backend is available
• Graceful fallback to stub when backend unavailable