Cache next entry arguments

[adzialocha]

Since we introduced querying the next entry arguments based on document view ids the old caching logic didnt't work anymore, we need a new solution!

Caching keys were organized as ${publicKey}/${viewId}, which means that it will just make an entry in the cache after every next entry request - but never hit it afterwards, as the view id changes constantly with each request. The cache just fills up but is never really used.

To bring back caching we need to extend the API with something which allows us to handle document instances and either persist the document id across a whole session (easy) or record the whole operation graph locally as well (hard).

[adzialocha]

Sketchy idea for a high-level API (def. needs more thinking, but you get the idea):

const session = new Session('http://localhost:2020/graphql').setKeyPair(new KeyPair());
const document = new Document('chat_0020...');

const viewId = await document.create({
  message: 'Hello, new API',
}, session);

await document.update({
  message: 'This UPDATE was using cached next entry arguments',
}, session);