vCon Extension for SIP Signaling and STIR/SHAKEN Data

This document defines a vCon extension for capturing Session Initiation Protocol (SIP) signaling metadata, STIR/SHAKEN certificate data, and related telephony information within the vCon conversation data container. The extension uses the vCon Attachment Object to store SIP messages and certificates, and introduces optional parameters on Party and Dialog Objects to carry SIP-specific identifiers. This extension is classified as Compatible per the vCon extension framework, allowing implementations that do not recognize it to safely ignore the additional data.