fix: sd-jwt vc sub value

This PR aims to resolve the issue #276

docs/en/pid-eaa-data-model.rst

@@ -85,7 +85,7 @@ The following claims MUST be in the JWT payload. Some of these claims can be dis
       - [NSD].URL string representing the PID/(Q)EAA Issuer unique identifier.
       - `[RFC7519, Section 4.1.1] <https://www.iana.org/go/rfc7519>`_.
     * - **sub**
-      - [NSD].Thumbprint of the JWK in the ``cnf`` parameter.
+      - [NSD].The identifier of the subject of the Digital Credential, the User, must be opaque and should not correspond to any anagraphic data or be derived from the User's anagraphic data through pseudonymization.
       - `[RFC7519, Section 4.1.2] <https://www.iana.org/go/rfc7519>`_.
     * - **iat**
       - [SD].UNIX Timestamp with the time of JWT issuance, coded as NumericDate as indicated in :rfc:`7519`.