Reviewer Ellie: Add logs if HSS gives us an IRS that doesn't contain a SIP URI

Tests whether the IRS returned by the HSS (in either an SAA or a PPR) contains a SIP URI. If it doesn't, raise an error log and a SAS log before continuing as normal.

Includes a PPR UT checking the log gets raised.

All the existing UTs run fine.
Do you actually need to check the ppa? It's not what you're testing in this UT