Add BearerTokenFunc to support dynamic bearer token authentication
for OTLP gRPC exporters. Tokens are injected via gRPC PerRPCCredentials
on each export request.
- Add BearerTokenFunc type and Config field in tracerconfig
- Implement bearerCredentials (gRPC) and bearerRoundTripper (HTTP)
- Wire bearer auth into all three gRPC exporter creation functions
- Add token verification before flushing buffered logs
- Fix race condition in buffering exporter initialization
Note: HTTP exporters don't support dynamic bearer tokens due to
OpenTelemetry SDK limitations (no WithHTTPClient option). Use gRPC
protocol for dynamic tokens.
Remove sync.Once reset that caused "unlock of unlocked mutex" panic.
Redesign initialization to use only checkReadiness goroutine for
retry attempts, eliminating race condition while preserving retry
functionality for TLS/tracing setup delays.
Add buffering exporter to queue OTLP logs until tracing is configured.
Support TLS configuration for OpenTelemetry log export with client
certificate authentication. Improve logfmt formatting and tracing setup.
