PushNotification: Make 'devices' field optional

[vanyasem]

Fixes #1947

[CLAassistant]

All committers have signed the CLA.

[krille-chan]

According to https://spec.matrix.org/v1.12/push-gateway-api/#post_matrixpushv1notify this is wrong. The devices field is required

[vanyasem]

@krille-chan the documentation that you linked specifies the JSON model for the API endpoint /_matrix/push/v1/notify, for which the devices field is indeed mandatory

You misunderstood the meaning of the model linked above. It's a server-side model for the Push Gateway itself. It's not meant to be sent back to users devices

sygnal is a reference Push Gateway by the Matrix Foundation

The definition of "reference" is:

A software example of a specification, intended to help others implement their own version of the specification or find problems during the creation of a specification.

You can learn more about the meaning of a "reference implementation" here: https://en.wikipedia.org/wiki/Reference_implementation

Arguing that an official reference implementation is somehow wrong, and your specific interpretation of the documentation is right is really bold.

Just to be sure, the field in question has been discussed directly with the Matrix team, and they confirmed that devices is only mandatory on the server-side, and that it makes no sense to include it in the model when sending a notification back to the device. See matrix-org/sygnal#319 for more details

Your implementation is the only one that does that, yet you still choose to stand by your incorrect interpretation of the docs.

[vanyasem]

Btw the correct documentation to link would be https://github.com/matrix-org/sygnal/blob/main/docs/applications.md#firebase-cloud-messaging, which specifies the client-side model for the push:

{
  "event_id": "$3957tyerfgewrf384",
  "type": "m.room.message",
  "sender": "@exampleuser:example.org",
  "room_name": "Mission Control",
  "room_alias": "#exampleroom:example.org",
  "sender_display_name": "Major Tom",
  "content_msgtype": "m.text",
  "content_body": "I'm floating in a most peculiar way.",
  "room_id": "!slw48wfj34rtnrf:example.org",
  "prio": "high",
  "unread": "2",
  "missed_calls": "1"
}