Use PostgresNIO's default JSON coders
This patch was authored by @jordanebelanger and released by @tanner0101.
This adds support for using non-Foundation JSON coders when decoding and encoding JSON columns (#195).
For example, if you want to use the pure-swift JSON coders, you can now do this during the configuration of your application:
import PureSwiftJSON
PostgresNIO._defaultJSONDecoder = PSJSONDecoder()
PostgresNIO._defaultJSONEncoder = PSJSONEncoder()
Do note that the JSON coders used here MUST be thread safe internally.