Module trace_layer 

Trace propagation utilities for Problem responses

This module provides helper traits and functions to automatically enrich Problem with trace context:

• trace_id: extracted from the current tracing span
• instance: extracted from the request URI

This eliminates per-callsite boilerplate and ensures consistent error reporting.

Traits

WithRequestContext

Middleware-friendly: enrich errors from Axum extractors

WithTraceContext

Helper trait for enriching Problem with trace context