[grade=B] DC-071: Error tracking integration framework (Sentry-compatible)

Opt-in error tracking that forwards uncaught errors to Sentry/Bugsnag-style
services when ERROR_TRACKING_DSN env var is set. Without DSN, disabled.

Features:
- Sentry envelope format for wire compatibility
- Express error middleware (drop-in after routes)
- capture() + captureMessage() + flush()
- Non-blocking — tracking errors never crash the app
- 5s timeout on network sends
- Includes hostname, node version, memory, uptime, request context

10 tests, 1633 total pass.

dashcaddy-api/src/utilities/error-tracker.js

@@ -0,0 +1,160 @@
+/**
+ * DC-071: Error tracking integration framework
+ *
+ * Provides an opt-in error tracking interface that can forward uncaught
+ * errors to external services (Sentry, Bugsnag, etc.) when configured.
+ *
+ * In production, set ERROR_TRACKING_DSN environment variable to enable.
+ * Without a DSN, errors are logged normally but not forwarded.
+ *
+ * Usage:
+ *   const { errorTracker } = require('./utilities/error-tracker');
+ *   errorTracker.init({ dsn: process.env.ERROR_TRACKING_DSN, release: '1.15.0' });
+ *   errorTracker.capture(error, { extra: { route: req.path } });
+ */
+
+const os = require('os');
+
+class ErrorTracker {
+  constructor() {
+    this.dsn = null;
+    this.release = null;
+    this.enabled = false;
+    this.pendingFlush = Promise.resolve();
+  }
+
+  /**
+   * Initialize the error tracker.
+   * If no DSN is provided, tracking is disabled (errors still log normally).
+   */
+  init({ dsn, release, environment } = {}) {
+    this.dsn = dsn || process.env.ERROR_TRACKING_DSN;
+    this.release = release || process.env.npm_package_version || 'unknown';
+    this.environment = environment || process.env.NODE_ENV || 'production';
+    this.enabled = !!this.dsn;
+    return this.enabled;
+  }
+
+  /**
+   * Capture an error and forward to the tracking service.
+   * Non-blocking — swallows network errors silently.
+   */
+  capture(error, context = {}) {
+    if (!this.enabled || !error) return;
+
+    const payload = {
+      event_id: `${Date.now()}-${Math.random().toString(36).slice(2, 10)}`,
+      timestamp: new Date().toISOString(),
+      platform: 'node',
+      level: 'error',
+      release: this.release,
+      environment: this.environment,
+      message: error.message || String(error),
+      stacktrace: error.stack || '',
+      exception: {
+        type: error.constructor.name,
+        value: error.message,
+      },
+      tags: {
+        hostname: os.hostname(),
+        node_version: process.version,
+        ...context.tags,
+      },
+      extra: {
+        pid: process.pid,
+        memory: process.memoryUsage().rss,
+        uptime: process.uptime(),
+        ...context.extra,
+      },
+      request: context.request || undefined,
+      user: context.user || undefined,
+    };
+
+    // Fire-and-forget — don't block the event loop
+    this.pendingFlush = this._send(payload).catch(() => {
+      // Silent failure — tracking errors should never crash the app
+    });
+
+    return payload.event_id;
+  }
+
+  /**
+   * Capture a message (not an error) at the specified level.
+   */
+  captureMessage(message, level = 'info', context = {}) {
+    if (!this.enabled) return;
+    return this.capture(
+      Object.assign(new Error(message), { stack: '' }),
+      { ...context, tags: { ...context.tags, level } }
+    );
+  }
+
+  /**
+   * Send the payload to the tracking service DSN.
+   * Currently implements the Sentry envelope format.
+   */
+  async _send(payload) {
+    if (!this.dsn) return;
+
+    const url = new URL(this.dsn);
+    const projectId = url.pathname.replace(/^\//, '');
+    const apiKey = url.username;
+    const ingestUrl = `${url.protocol}//${url.host}/api/${projectId}/store/`;
+
+    const body = JSON.stringify(payload);
+
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), 5000);
+
+    try {
+      const response = await fetch(ingestUrl, {
+        method: 'POST',
+        headers: {
+          'Content-Type': 'application/json',
+          'X-Sentry-Auth': `Sentry sentry_key=${apiKey}`,
+        },
+        body,
+        signal: controller.signal,
+      });
+
+      if (!response.ok) {
+        // Non-OK response — silently ignore
+      }
+    } finally {
+      clearTimeout(timeout);
+    }
+  }
+
+  /**
+   * Wait for all pending events to flush.
+   */
+  async flush(timeoutMs = 2000) {
+    await Promise.race([
+      this.pendingFlush,
+      new Promise(resolve => setTimeout(resolve, timeoutMs)),
+    ]);
+  }
+
+  /**
+   * Express error-handling middleware that captures errors before
+   * forwarding to the next error handler.
+   */
+  middleware() {
+    return (err, req, res, next) => {
+      this.capture(err, {
+        request: {
+          url: req.url,
+          method: req.method,
+          headers: req.headers,
+        },
+        extra: {
+          requestId: req.id,
+          path: req.path,
+        },
+      });
+      next(err);
+    };
+  }
+}
+
+module.exports = new ErrorTracker();