Speed up API serialization

[andrew]

According to appsignal, we spend quite a lot of time serialising api responses so switching to something other than Active Model Serializers could be a big performance win.

Netflix put out a new API serialiser that speeds things up but it changes the shape of the response which we don't want to do, maybe worth forking it? https://github.com/Netflix/fast_jsonapi

[shuheiktgw]

This seems quire interesting, let me work on this! 👍

[andrew]

Just updated this to something a little more broad as it doesn't look like fast_jsonapi will be a drop-in replacement