Actually I wonder about removing those custom reads...
It was a choice I had done explicitly while implementing the autosource for ReactiveMongo.
You have a default `Reads[T]` which is generally created by the macro and that you use in your business logic inside the server.
But then whe you may have a custom Reads[T] that is used to read Json coming from outside of your server.

It's really useful for ReactiveMongo but maybe not for Datomic so maybe we can get rid of it for Datomic implementation... 

limitReader/pageSizeReader/skipReader were useful if the datomic query was sent in a datomic Get with a body and not in the query parameters. It can be useful sometimes to prevent have too long querystring.