[WIP] feat: Send transactions in envelopes

The new Envelope endpoint and format is what we want to use for
transactions going forward.

TODO: include rationale.

Author: rhcarvalho

packages/node/src/transports/base.ts

@@ -84,7 +84,26 @@ export abstract class BaseTransport implements Transport {
     }
     return this._buffer.add(
       new Promise<Response>((resolve, reject) => {
-        const req = httpModule.request(this._getRequestOptions(), (res: http.IncomingMessage) => {
+        const options = this._getRequestOptions();
+        let payload = JSON.stringify(event);
+
+        if (event.type === 'transaction') {
+          options.path = (options.path || '').replace('/store', '/envelope');
+          (options.headers || {})['content-type'] = 'application/x-sentry-envelope';
+
+          const enveloperHeaders = JSON.stringify({
+            event_id: event.event_id,
+            sent_at: null,
+          });
+          const itemHeaders = JSON.stringify({
+            content_type: 'application/json',
+            type: event.type,
+          });
+          const envelope = `${enveloperHeaders}\n${itemHeaders}\n${payload}\n`;
+          payload = envelope;
+        }
+
+        const req = httpModule.request(options, (res: http.IncomingMessage) => {
           const statusCode = res.statusCode || 500;
           const status = Status.fromHttpCode(statusCode);
 
@@ -118,7 +137,7 @@ export abstract class BaseTransport implements Transport {
           });
         });
         req.on('error', reject);
-        req.end(JSON.stringify(event));
+        req.end(payload);
       }),
     );
   }