[QUESTION]: deleteFromCacheById doesn't work for findByFields

[simplecommerce]

Hi,

I haven't used it yet, but I noticed that deleteFromCacheById only works when used with findOneById.
In the code, it doesn't seem to work for findByFields.

Can you confirm?

[lorensr]

Confirmed. This is the key if you'd like to delete the cached results of findByFields:

https://github.com/GraphQLGuide/apollo-datasource-mongodb/blob/master/src/cache.js#L131

I'd also be happy to receive a PR for deleteFromCacheByFields.