RIght now whether a warmer is blocking on startup or not is defined in the actual warmer itself. This is misleading, because if you then use Cachex.warm/2, you're able to warm it in the opposite way (ignoring the definition).

The way to approach this is to change the signature of warmers in the cache record to look something like this:

warmers(required: [], lazy: [])

Having them named and organized in this way makes the warmer definition clearer, and makes it clear that it can be overridden per warmer. I don't like the names above, but they're WIP until I come up with something better.

This is obviously a breaking change and as such will be included in 4.0.