Function init_observability 

pub fn init_observability(
    logging_config: &StructuredLoggingConfig,
    otel_config: Option<&ObservabilityConfig>,
    service_name: &str,
    environment: &str,
    log_level: &str,
) -> Result<(LogBuffer, OtelShutdownGuard), Error>

Unified observability initialization.

Combines structured logging (fmt layer) and optional OpenTelemetry tracing into a single global subscriber. This replaces the old pattern of calling init_structured_logging() + init_tracing_with_otel() separately, which caused a double-subscriber bug where the second set_global_default call silently failed and the OTel layer was never active.

Arguments

• logging_config — Structured logging settings (JSON/pretty, fields, buffer)
• otel_config — Optional OTel configuration. When Some and tracing_enabled, an OTel layer is added (with optional OTLP exporter).
• service_name — Identifies the service in logs and traces.
• environment — e.g. “development”, “production”.
• log_level — Filter directive such as “info” or “backbone=debug”.