Convert Slack's @channel and @here to @room

[thomas-profitt]

@channel and @here evidently do slightly different things in Slack, but we can forget the nuance and just convert both.

https://github.com/matrix-hacks/matrix-puppet-slack/pull/32 does not adequately address the issue because:

• It does not handle @here, only @channel (unless Slack converts @here to <!channel> like it does @channel in the payload we get from its API)
• Because our ghost rooms are created without specifying that level-0 users should be able to @room, and our ghost users are power level 0, the notification doesn't actually fire.

[thomas-profitt]

Here's some documentation on how the room API's power levels option expects its data right now:

{
    "events_default": 0,
    "invite": 0,
    "state_default": 50,
    "redact": 50,
    "ban": 50,
    "kick": 50,
    "notifications": {
      "room": 50,
    },
    "events": {
      "m.room.avatar": 50,
      "m.room.name": 50,
      "m.room.canonical_alias": 50,
      "m.room.history_visibility": 100,
      "m.room.power_levels": 100
    },
    "users": {
      "@example:matrix.org": 100
    },
    "users_default": 0,
  }

Creating rooms with different configuration is something to be implemented in matrix-puppet-bridge, it's only the high-level requirement "we need @channel and @here turned into @room" that belongs here in matrix-puppet-slack's issues.

[thomas-profitt]

Update: We're now converting @channel and @here to @room, but still the ghosts don't have permission to actually notify.