I wrote a function handleOutboxNote that's supposed to do the whole outbox POST
handler process. There's an outbox item table in the DB now, I adapted things
in various source files. Ticket comment federation work is still in progress.
The custom module provides a parametric wrapper, allowing any specific
FromJSON/ToJSON instance to be used. It's a standalone module though, and not a
wrapper of persistent-postgresql, because persistent-postgresql uses aeson
Value and it prevents using toEncoding to get from the value directly to a
string.
