feat: siprect custom headers (#95)

* feat: siprect custom headers

* update siprec client utils

* wip

lib/call-session.js

@@ -733,6 +733,7 @@ Duration=${payload.duration} `
             const to = this.req.getParsedHeader('To');
             const aorFrom = from.uri;
             const aorTo = to.uri;
+            const headers = contentType === 'application/json' && req.body ? JSON.parse(req.body) : {};
             this.logger.info({to, from}, 'startCallRecording request for an outbound call');
 
             const srsUrl = req.get('X-Srs-Url');
@@ -771,7 +772,8 @@ Duration=${payload.duration} `
               del: this.del,
               blockMedia: this.blockMedia,
               unblockMedia: this.unblockMedia,
-              unsubscribe: this.unsubscribe
+              unsubscribe: this.unsubscribe,
+              headers
             }));
             try {
               succeeded = (await Promise.all(