Supervisor additions

Every Taffrail API request and response is archived in our Supervisor database. We designed Supervisor to help our clients comply with FINRA Rule 3110.

Today, we're introducing two new data points available for every API archived. Both properties are on the HTTP request.

1. referrer — indicates the host page from where the API is being called. It is captured automatically when using the Embed or can be provided by sending the Taffrail-Api-Referrer request header.
2. sessionId — associate archived records with a single user session for improved reporting and replay.