PSQLCodable protocol should be public.

[hjuraev]

PSQLCodable is a private protocol. Therefore, it won't allow us to create custom types. Please consider opening protocol to the public.

[0xTim]

The PSQLCodable protocol is currently internal along with all the new interface stuff in the New directory. That will be made public in a future release (see #188 )

To make your own types for the current release they just need to be Codable. See https://github.com/rabc/fluent-postgis/blob/master/Sources/FluentPostGIS/Geometry/PostGISDataType.swift for example