This new struct allows supporting unlimited number of ASPs per AS. It can also potentially be used in the future to: * Hold M3UA "ASP Identifier" per AS<->ASP association * Speed up iterating over AS served by a given ASP.
NOTE: Having >16 ASPs per AS may not be desirable, for instance under loadshare traffic mode ITU SLS is 4 bit, so despite having ext_sls extending the table to 128 entries based on OPC, it may not provide enough entropy to properly loadshare among all of them.
This way we can iterate easily/quickly the AS served by a given ASP. This in turn allows simplifying some code since we cache the amount of AS served by the ASP at any time, so we save some counting.
Look for counterpart on the object with the shortest list, ie. convert from O(N) to O(min(N,M)). This way eg. if we have 100 ASPs on 1 AS, lookup time becomes O(1). Same if we have eg. 1 ASP serving 100 AS.
If configured, it will be transmitted during ASP UP and ASP UP ACK. This may be needed if facing an SG/IPSP peer who requires ASP Identifier to be set.
xua_asp_fsm: Error on ASP UP (ACK) with non-unique ASP Identifier
Following RFC4666: """ The "Invalid ASP Identifier" error is sent by an SGP in response to an ASP Up message with an invalid (i.e., non-unique) ASP Identifier """
