Event Comments - Githubissues

Add comments section for events

API

[x] POST/GET /events/{id}/comments
Event to return all comment ids (always) + last 10 & all unread messages (members), more
Comments load when event detail or comments in event detail is open
- Use limit 10/unread and then a full if opened?

Comments load with GET /events/{id}/comments on detail screen (can add limit / unread)
Comment count in event list item / detail
- Unread badge (adds to total in drawer)
Comment store
- Required to use relatedEntities with event easily
- [x] Comment entity to have a @computed returning whether currentUser is in seenBy
- [ ] ~~Track read comments in a persistent collection of ids
- add to CommentStore.seen persistent collection
  - set a delay at the end of loadComments, after X sec mark rendered comments read in store & sync to api
- diff can be used to show unread comments~~
- Split into #121
Comments visible as a small view at the bottom with
- few last messages shown
- quick reply button that opens a modal autofocused to type
- expand button or slide up to open which shows a "bottom sheet" with messages & starts async load of more messages

author,eventId,timestamp,messageId,message,seenBy

seenBy allows showing # of unread messages
- PUT /events/{id}/comments/seen?ids[]=1&ids[]=2&... when read