Set max size to gridUnits * 30. The aim is to allow them to be generally bigger than bubble mode but not so huge that they take up the entire screen
BUG: 454878
**Updated**
Add a section label at the top which shows the date label of the next section up. This means that the user will always be able to see the date of all messages on screen.

From the feedback given I've added a background at the top. I also added an underline to the heading which applies both at the top and in the listView since they use the same component. I added it originally for the top because I felt it looked a bit weird having messages appear from behind a heading background the same colour as the listView background.
Note: I know the gaps between messages are not right. I had to set the spacing in the listView to 0 to prevent itemAt returning null. I plan to add it back in as part of the delegate code before it would be merge.
Fixes BUG:454880
Initial work to create a model so that new servers can be added to the list.
The model will also check if the server is valid before allowing it to be added.
Implements network/neochat#11
### TODO
- [x] Add functionality to cache added servers
Replace the RowLayout with a ComboBox. This permits a higher number
of accounts to be used in the application without reducing the
usability.
BUG: 460601
Stop stripping paragraph tags as this is causing line breaks to be removed in the formatted body. Any double new line in the plain text is treated as a paragraph in rich text.
BUG: 458800
This is the start of a significant refactoring of everything related to sending messages, which is roughly:
- the chatbox
- action handling
- message sending on the c++ side
- autocompletion of users/rooms/emojis/commands/things i forgot
Notable changes so far include:
- ChatBox is now a ColumnLayout. As part of this, i removed the height animations for now. <del>as far as i can tell, they were broken anyway.</del> I'll readd them later
- Actions were refactored to live outside of the message sending function and are now each an object; it's mostly a wrapper around a function that is executed when the action is invoked
- Everything that used to live in ChatBoxHelper is now in NeoChatRoom; that means that the exact input status (text, message being replied to, message being edited, attachment) is now saved between room switching).
- To edit/reply an event, set `NeoChatRoom::chatBox{edit,reply}Id` to the desired event id, `NeoChatRoom::chatBox{reply,edit}{User,Message}` will then be updated automatically
- Attachments behave equivalently with `NeoChatRoom::chatBoxAttachmentPath`
- Error message reporting from ActionsHandler has been fixed (same fix as in !517) and moved to NeoChatRoom
Broken at the moment:
- [x] Any kind of autocompletion
- [x] Mentions
- [x] Fancy effects
- [x] sed-style edits
- [x] last-user-message edits and replies
- [x] Some of the actions, probably
- [x] Replies from notifications
- [x] Lots of keyboard shortcuts
- [x] Custom emojis
- [x] ChatBox height animations
TODO:
- [x] User / room mentions based on QTextCursors instead of the hack we currently use
- [x] Refactor autocompletion stuff
- [x] ???
- [x] Profit