Replace all REST query empty result HTTP Status codes to 200

[fedekunze]

Summary

Replace all query empty results HTTP Status codes to 200 (OK)

Problem Definition

I've seen in several places in the gov module and in other files that the returned status code we are using for an empty search (i.e. query) result are 500 (Internal Server Error), 204 (No Content) or 404 (Not Found).

Proposal

Replace all for status 200 (OK), since it's the standard to handle that situation.

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[jackzampolin]

I like this idea quite a bit!