* Add a replication test suite
* Allow overriding the default destination for read queries when using replication
For many applications that want to use read slaves, data consistency isn't super important, and so all reads can be sent by default to a read slave. For some applications though, it's only select queries that can be sent to read slaves as end-users of the application expect data consistency almost everywhere. This new setting lets apps like those change the default such that query builders need to opt *in* to sending to a read slave, instead of opt out.
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