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.
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