Synthetic ID and Fresh ID Incorrectly Behave the Same #51

We need to look at the code in crates -> common -> src -> synthetic.rs to find out why the 2 headers behave the same. SyntheticID should keep its hash ID once its set until expiration or cookie deletion and freshID should change based on IP address moving around (mobile, wifi, office, etc).

so we want x-synthetic-trusted-server hmac injected into its custom header (for downstream and initial page load) and appended to 1st party cookie (look at auburndao.com w/ network tools).

FYI: this will be another ticket regarding consent behavior, but for context, we need to respect CMP and cookie opt-in and opt-out, so if they opt out, we cannot set header, and only sometimes 1st party cookie.

if x-synthetic-ts is present in a header, or cookie, then re-use it.

x-fresh-id should be recalculated when the IP address changes, so can we do this without having to recalc the hmac each time? It may be more expensive to do it anyway but this?

x-synthetic-ts should have a lifetime so lets choose 7 days for now