During triggering, the S-CSCF currently does not save the initial request information needed to identify the session after it gets triggered through B2BUA ASs.

This presents limitations such as:
- if a B2BUA doesn't include P-Asserted-Identity in the 2nd leg, currently the S-CSCF says: S-CSCF:S_save_dialog(): Error retrieving orig contact
- it is not possible to detect that an AS changed the Request-URI in the terminating case. According to TS 24.229, the S-CSCF should foward based on the Req-URI when it gets changed by an AS in the terminating case, and not proceed with following triggers for the called user.

We need:
- to store at least the P-Asserted-Identity for the MO triggering and the Request-URI for the MT triggering with the initial request ISC marking state
- encode the original dialog identifier to enable retrieval of this info in subsequent triggers.