story(machine): implement DELETE /api/v1/machines/{id} endpoint

[Zaba505]

Description

Implement HTTP REST API endpoint for deleting a machine registration. This allows administrators to remove machines from the inventory when they are decommissioned or no longer managed.

Acceptance Criteria

• Endpoint created in services/machine/endpoint/delete_machine.go
• Route: DELETE /api/v1/machines/{id}
• Implements OpenAPI-first handler pattern (z5labs/humus):
  • RequestBody() method defining OpenAPI request schema
  • Responses() method defining OpenAPI response schemas
  • ServeHTTP() method implementing HTTP handler logic
• Path parameter validation:
  • Extract machine ID from path
  • Validate UUIDv7 format
  • Return HTTP 400 Bad Request with RFC 7807 Problem Details for invalid format
• Machine existence check:
  • Query Firestore to verify machine exists
  • Return HTTP 404 Not Found with RFC 7807 Problem Details if not found
• Firestore integration:
  • Delete machine from machines/{id} collection
  • Handle Firestore errors gracefully
  • Consider soft delete vs hard delete (optional: archive to deleted_machines collection)
• Response:
  • HTTP 204 No Content on success
  • Empty response body
• Error responses use RFC 7807 Problem Details format:
  • Content-Type: application/problem+json
  • Include type, title, status, detail, instance fields
  • 404 response includes machine_id field
• Idempotency:
  • Deleting an already-deleted machine returns 404 (not 204)
  • Consider idempotency for concurrent delete requests
• OpenTelemetry instrumentation:
  • Log machine deletion with machine_id
  • Metrics: deletion count, success/failure rate
  • Trace context propagation
• Unit tests:
  • Test successful machine deletion
  • Test machine not found (404)
  • Test invalid machine ID format (400)
  • Test idempotency (delete twice)
  • Mock Firestore client
  • Test soft delete archiving (if implemented)

Related Issues

Part of Machine Service implementation
Related to API documentation in docs/content/r&d/services/machine-mgmt/delete-machine.md