stbx-core: Manually write Transaction JSON codecs

[epost]

We need to do a bit more around optional/singleton fields than the automatic derivation will give us, for example around the fields:

• ?: message
• wiring:
  • placeNames
    • update 2019-09-12: Jelle said we'll probably want to do things like placeNames using net labelings according to mapping schemas in the future, rather than embedding them in the tx record like we do now.
• firing:
  • glued transition id (a singleton array) (this field is currently called path)

/cc FYI @marcosh, because you'll need encoders at some point.

[marcosh]

👍

[marcosh]

I noticed that https://github.com/paf31/purescript-foreign-generic version 9 does not have the ability to decode record automatically, while version 10 does. This requires updating Purescript to version 0.13

[epost]

@marcosh Ah, but we don't use that; we use argonaut. Additionally, I'm just hand-writing decoders because we have special requirements re missing fields; they need to result in a Nothing field value instead of a decoding error.

[marcosh]

ah, ok, thanks! I'll take a look at that