Introduces the `AddEnvelopeReceiver` method in the `Extension` class to add envelope receivers with parameters for UUID, email, salutation, and optional phone. Also adds the `EnvelopeReceiverAddReadSQL` class implementing `ISQL<Envelope>`, containing a SQL query to create a new receiver using the stored procedure `PRSIG_API_CREATE_RECEIVER`. Includes XML documentation for improved code readability and maintainability.