Add an option to toggle whether a room is a direct chat or not

This is useful if you accidentally created a room with someone, but not
as a "direct chat". Since this is a weird option, I stuck it under
developer tools for now but it could possibly surface into the regular
UI in the future.

src/devtools/RoomData.qml

@@ -36,10 +36,25 @@ ColumnLayout {
                 dialog.chosen.connect(id => root.room = root.connection.room(id))
             }
         }
+        FormCard.FormDelegateSeparator {}
         FormCard.FormTextDelegate {
             visible: root.room
             text: i18n("Room Id: %1", root.room.id)
         }
+        FormCard.FormDelegateSeparator {}
+        FormCard.FormCheckDelegate {
+            visible: root.room
+            text: i18nc("@option:check Toggle for whether this room is considered a direct chat or not", "Direct Chat")
+            checked: root.room.isDirectChat()
+            enabled: root.room.totalMemberCount === 2
+            onCheckedChanged: {
+                if (checked) {
+                    root.room.markAsDirectChat();
+                } else {
+                    root.connection.removeFromDirectChats(root.room.id);
+                }
+            }
+        }
     }
     FormCard.FormHeader {
         title: i18n("Room Account Data")