Urql: RFC: Make "consumer" components reactive to cache changes

[kitten]

In the next branch we already moved a lot of the caching logic to an exchange. It's basically almost equivalent. If we now introduce a more complete "watching" mechanism, then components can react to changes in the cache, which allows us to move all caching logic to an exchange and completely remove it from components.

This also has the nice side-effect of users being able to introduce 100% new caching logic via a custom cache exchange. This could pave way for a normalized cache a la Apollo, which is opt-in as an exchange.

cc @kenwheeler: Let's discuss the potentials of this and its feasibility pre-0.3?

[kenwheeler]

Let's chat today about the implications

[blorenz]

How'd this go?

[kitten]

@blorenz really well! This branch (let’s call it next-next 😂) has no caching logic anywhere but the cacheExchange, which makes it possible to write custom caching logic for urql https://github.com/FormidableLabs/urql/pull/98