Update the UX to refer to structure direct chats as friends. The direct chats are pulled into their own tab in the space drawer.
The `UserDetailDialog` is also updated to check whether a direct chat already exists and if not ask to invite as friend.

Since this means that the space drawer can no longer be hidden when there are no spaces,
also make it less empty by adding a button for creating new spaces.
More things will come in the future.
BUG: 479051
After downloading a file, the model calls the extractor and uses the
JSON to show some basic information about the content and allows to import
the data to Itinerary. This is entirely runtime-optional; no build-time dependencies
are required and nothing changes if the extractor isn't available.
Directly calling signals is the supported way to send signals.
Calling signal handlers worked in the past, but will be phased out in
the future (https://bugreports.qt.io/browse/QTBUG-120573).
Refactor `LinkPreviewer` to take an event and put the functions for getting the link in the class itself. This means the functions in `EventHandler` are no longer required.
This mr also sets up `LinkPreviewer` so that it is automatically updated when an event is edited. This includes changing the link if edited, and it can handle a message having a previous link removed or a one added when one didn't exist before.
Also adds test suite.
Currently we effectively create the reactions list in EventHandler then pass that data into a model. This reworks the model so that we just pass in a room and an event and it grabs it's own data. This means that:
- the functions in event handler are no longer required
- the model can update itself to add/remove reactions so no need to handle that in MessageEventModel
- MessageEventModel only needs to create new ReactionModels or remove old ones when no reactions exist anymore
A basic test suite has also been created for the ReactionModel
Refactor PollHandler to make it more reliable. This ended up with much more code than I expected as the original intent was just to stop a crash when switching rooms.
- Using a event string was flaky, changing to using an event reference is more reliable.
- Since we're only creating them from NeoChatRoom there is no need to to be able to set properties from QML so only read properties.
- Pass from the MessageEventModel rather than an invokable method.
- Create a basic test suite
- Create properties in PollHandler to remove the need to use content in PollDelegate, this means content is no longer a required role.