NAME
       sasl_user_exists - Check if a user exists on server
SYNOPSIS
       #include <sasl/sasl.h>
       int sasl_user_exists( sasl_conn_t *conn,
                             const char *service, const char *user_realm,
                             const char *user)
DESCRIPTION
       sasl_user_exists will check if a user exists on the server.
       conn a connection context
       service Service name or NULL (for service name of connection context)
       user_realm Realm to check in or NULL (for default realm)
       user User name to check for existence of.
RETURN VALUE
       Returns SASL_OK on success. SASL error code on failure.
CONFORMING TO
       RFC 2222
SEE ALSO
       sasl(3), sasl_errors(3)