Make client writeFragment and writeQuery behaviour consistent with cache

[andrebrantom]

This change makes the API and behaviour of ApolloClient::writeFragment consistent with that of Cache::writeFragment in that it returns the Reference of the changed object. This is useful if you have some cache manipulation functions that need to run either against the client in a hook or component, or in a mutation update() handler.

I created an issue here: https://github.com/apollographql/apollo-feature-requests/issues/319

[apollo-cla]

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[andrebrantom]

Apologies for letting this hang, I've just updated both writeQuery and writeFragment as suggested, I also updated DataProxy::writeFragment and DataProxy::writeQuery return types to match. Not sure if that might break something, but it means DataProxy can now be used to abstract either cache or client for writes.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 25e63ca513b3782f84c14d7c506ffc818e0591f9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@apollo/client	Patch

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