Handle multiple line names

Add function to get the display name for an author on a single line as nothing stops there being linebreaks.

BUG:476731

src/eventhandler.h

@@ -111,6 +111,17 @@ public:
      */
     QString getAuthorDisplayName(bool isPending = false) const;
 
+    /**
+     * @brief Get the display name of the event author but with any newlines removed.
+     *
+     * Turns out you can put newlines in your display name so we need to handle that
+     * primarily for the room list subtitle.
+     *
+     * @param isPending whether the event is pending as this cannot be derived from
+     *                  just the event object.
+     */
+    QString singleLineAuthorDisplayname(bool isPending = false) const;
+
     /**
      * @brief Return a QDateTime object for the event timestamp.
      */