feat(audit): Internal audit API client for service-to-service communication

[nycomp]

Summary

Adds internal HTTP client campus.audit.client for communication between campus.auth/campus.api deployments and the audit service. This enables the tracing middleware (issue #428) to send trace spans via HTTP.

Changes

New Files

• campus/audit/client/__init__.py - AuditClient entry point with environment-based URL resolution
• campus/audit/client/interface.py - Base classes: ResourceRoot, ResourceCollection, Resource
• campus/audit/client/v1/__init__.py - v1 API module
• campus/audit/client/v1/root.py - AuditRoot resource
• campus/audit/client/v1/traces.py - Traces, Trace, Spans, Span resources

Modified Files

• campus/audit/middleware/tracing.py - Updated to use new client API (new() instead of ingest())

API Design

Follows Campus API schema conventions matching campus-api-python:

• ResourceCollection for collections with trailing slash paths (path = "traces/")
• Nested classes for individual items (Traces.Trace, Traces.Spans.Span)
• Standard verbs: new(), list(), search(), get()
• Bracket access for IDs: client.traces[trace_id]
• Property access for named sub-resources: client.traces[trace_id].spans

Usage Example

from campus.audit.client import AuditClient

client = AuditClient()

# Ingest spans
client.traces.new(span_data)           # Single
client.traces.new(s1, s2, s3)          # Batch

# List/search traces
client.traces.list(limit=10)
client.traces.search(path="/api/v1/users")

# Get trace tree
tree = client.traces[trace_id].get_tree()

# Get specific span
span = client.traces[trace_id].spans[span_id].get()

Related Issues

• Internal Audit API Client for Service-to-Service Communication #453 - Internal audit API client (tracking issue)
• Audit Phase 4: Tracing Middleware #428 - Phase 4: Tracing Middleware (parent)
• Audit deployment #424 - Audit deployment (grandparent)