Refactor input stuff

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

src/roommanager.h

@@ -8,6 +8,8 @@
 #include <QObject>
 #include <uriresolver.h>
 
+#include "chatdocumenthandler.h"
+
 class NeoChatRoom;
 
 namespace Quotient
@@ -29,6 +31,7 @@ class RoomManager : public QObject, public UriResolverBase
     /// This property holds whether a room is currently open in NeoChat.
     /// \sa room
     Q_PROPERTY(bool hasOpenRoom READ hasOpenRoom NOTIFY currentRoomChanged)
+    Q_PROPERTY(ChatDocumentHandler *chatDocumentHandler READ chatDocumentHandler WRITE setChatDocumentHandler NOTIFY chatDocumentHandlerChanged)
 
 public:
     explicit RoomManager(QObject *parent = nullptr);
@@ -64,6 +67,9 @@ public:
     /// Call this when the current used connection is dropped.
     Q_INVOKABLE void reset();
 
+    ChatDocumentHandler *chatDocumentHandler() const;
+    void setChatDocumentHandler(ChatDocumentHandler *handler);
+
     void setUrlArgument(const QString &arg);
 
 Q_SIGNALS:
@@ -98,6 +104,8 @@ Q_SIGNALS:
     /// Displays warning to the user.
     void warning(const QString &title, const QString &message);
 
+    void chatDocumentHandlerChanged();
+
 private:
     void openRoomForActiveConnection();
 
@@ -106,4 +114,5 @@ private:
     QString m_arg;
     KConfig m_config;
     KConfigGroup m_lastRoomConfig;
+    ChatDocumentHandler *m_chatDocumentHandler;
 };