Support for simple caching

The client should support a simple caching mechanism (not as complex as Apollo client [1], more like a simple default config that improves simple default setups).

TODO: define how this should exactly work

[1]
https://www.apollographql.com/docs/react/data/queries/#supported-fetch-policies https://www.apollographql.com/docs/react/caching/cache-configuration/

Begin by reviewing the requested simple caching behavior and the linked Apollo fetch-policy and cache-configuration references. The issue first needs an agreed design defining the default configuration, cache behavior, and scope; work is done when those decisions are documented as actionable requirements.

Written by the indexing model from the issue text.