[Logs SDK] Log Appender for spdlog

[lalitb]

spdlog is one of the commonly used logging framework for C++, and it would be good to have the logging appender for the framework using logging bridge API.

More details:

Bridge API specs - https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/bridge-api.md
Bridge API implementation - https://github.com/open-telemetry/opentelemetry-cpp/tree/main/api/include/opentelemetry/logs
Implementing sinks in spdlog - https://github.com/gabime/spdlog/wiki/4.-Sinks#implementing-your-own-sink

The implementation should be part of the opentelemetry-cpp-contrib repo under the instrumentation directory.

[github-actions]

This issue was marked as stale due to lack of activity.

[nirb-s1]

having a stdlog sink to OTLP (OTEL collector over HTTP or GRPC) can be awesome!

[marcalff]

Closing, this is now implemented in opentelemetry-cpp-contribs.