Add function to parse analysis complete notification JSON

[adaluong]

This function makes it easier for downstream consumers (like package analysis) to parse the package analysis complete notification and identify the package being analysed.

Signed-off-by: Ada Luong adaluong@google.com

[oliverchang]

Is this still required?

[maxfisher-g]

@calebbrown do we need this code?

[calebbrown]

Long term - yes, I think this is the right place for this. Marshal/Unmarshal logic best exists next to the struct itself (e.g. url.Parse).

In this particularly case I am planning a small refactor in #651. So it's not critical to have this merged. Given the lack of unit tests we probably want to wait.