feat(notifications): groups

[GeopJr]

fix: #1191 #176

Very far from done.

[GeopJr]

it's getting shape but I still need:

1. do actual widgets, this 'fit group notifications in normal ones' is pretty bad
2. organize the version keeping mechs better
3. make sure the upgrade is seamless

[GeopJr]

I quite hate it because it's messy when you want to support both v1 and v2, but whatever at this point...

should be done

[GeopJr]

Some other stuff:

• I never noticed it before but it seems that the notifications websocket never emits updates and deletions. We need to deal with them however for privacy reasons (aka if someone mentions u and updates or deletes the post, youll still have it there...). To solve that we are forwarding events from the home websocket
• to_widget was marked as throwing an Oopsie. This was because it's an abstract method and we needed the empty one to always throw. But that's a programmer error if they haven't implemented it. The right solution is to assert instead, so we don't have to try and catch everywhere especially since we know it will never error.