Custom URL category support for SSL forward proxy

The allowlisting feature is extended to include custom URL categories supported by UTM in the allowlist configuration of SSL forward proxy. In this implementation, the Server Name Indication (SNI) field is extracted by the UTM module from client hello messages to determine the URL category. SNI is an extension of the SSL/TLS protocol. Each URL category has a unique ID. The list of URL categories in the allowlist is parsed and the corresponding category IDs are pushed to the Packet Forwarding Engine for each SSL forward proxy profile. The SSL forward proxy then determines through APIs whether to accept the proxy or to ignore the session.