Redux Toolkit: responseHandler should always be serializable

[gfortaine]

Addresses points brought up in https://github.com/rtk-incubator/rtk-query/issues/154

We have a use case where we need to consume the headers of the response. It looks like that we could handle this case through responseHandler by returning the raw Response : (response) => response. However, it seems that Redux Toolkit complains when responseHandler is a function (because it is not serializable). Thus, it appears that a suitable approach would be to simply add 'raw' as a potential responseHandler type, then to handle the raw Response with transformResponse (see corresponding tests).

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[phryneas]

I'll take a look tomorrow. It seems reasonable, but I want to check if we don't have other options that lead the the same pitfall. You have seen that you can use the codesandbox build above meanwhile?

[gfortaine]

OK, looking forward to your review tomorrow 👌By the way, many thanks for the codesandbox tip, I hadn’t seen it 👍

[phryneas]

Unfortunately, there's a bunch of other options with the same problem. I've opened #156 to try and find a more broad solution. Can you take a look please?

[gfortaine]

Solved by #156