Custom keyfields like Apollo InMemoryCache

I have some objects which don't use `id` as the key but some other fields and some objects where the id is not unique so I would like to disable de-duplication for them.

Is there a way to support a similar config as InMemoryCache to disable the de-duplication for them based on __typename?

Also Apollo supports both `id` and `_id` by default, can this module match the behaviour or atleast provide an option for default key name?

Use Apollo InMemoryCache as the reference behavior described in the issue. Define how configuration keyed by __typename should select custom key fields or disable de-duplication, and whether id and _id should be supported by default or through an option. Done means these cases are specified and covered by the project's relevant tests.

Written by the indexing model from the issue text.