[REFACTOR] current-state event: Change note format

[wowawiwa]

Currently, the current-state event includes the key notes: {[clientId: string]: Note[]};
Suggestion: notes: Note[]

The mapping from clientID isn't needed, as the author is inside the note already and we don't operate by clientID anyway in the frontend.

[abustany]

In that case the backend could send all notes in a flat list yes, since as you say the author ID is anyway embedded in the notes. The current shape actually just mirrors the datastructure used internally by the backend (ie. I didn't put more thought into it), but changing it is no problem at all!

[wowawiwa]

Or we can have all normalized.