SFC Non-transparent SF

Service Functions (SF) that do not support SFC encapsulation, such as NSH, require
an SFC Proxy to re-classify a packet that is returned from the egress port of the
SF. The SFC Proxy uses the N-tuple values of a packet header to re-classify a packet.
However, if the SF is non-transparent (it modifies a part of the N-tuple of a packet),
then re-classification cannot be done correctly.
See https://datatracker.ietf.org/doc/draft-song-sfc-legacy-sf-mapping/

This blueprint provides a mechanism for configuring the SFC Proxy to account for the N-tuple translation of the SF.