This generates random uuids for both each build run, and the app itself. It then propagates the app uuid through each subsequent build by serializing it into the cache.

This isn't completely ideal because PR apps will each get their own app uuid, but it should still allow us to do better analysis on our log data than we currently can.

Questions like "How many apps failed yesterday?" vs "How many builds failed yesterday"?

The build uuid helps make sure that we aren't ever double counting events somehow.