Gerrit: Factor out user parsing

This has several advantages:
1. It removes duplicate logic.
2. It is now clear where we use username and where full name.
3. Reviewers now appear with full names (broke by
   9f697128c3).

Change-Id: I5729abc9006cec0d0cb615b01c8ace5def60ce27
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/git/gerrit/gerritmodel.h

@@ -25,6 +25,8 @@
 
 #pragma once
 
+#include "gerritparameters.h"
+
 #include <QStandardItemModel>
 #include <QSharedPointer>
 #include <QDateTime>
@@ -35,8 +37,6 @@ QT_END_NAMESPACE
 
 namespace Gerrit {
 namespace Internal {
-class GerritServer;
-class GerritParameters;
 class QueryContext;
 
 class GerritApproval {
@@ -45,8 +45,7 @@ public:
 
     QString type; // Review type
     QString description; // Type description, possibly empty
-    QString reviewer;
-    QString email;
+    GerritUser reviewer;
     int approval;
 };
 
@@ -76,9 +75,7 @@ public:
     int dependsOnNumber = 0;
     int neededByNumber = 0;
     QString title;
-    QString owner;
-    QString user;
-    QString email;
+    GerritUser owner;
     QString project;
     QString branch;
     QString status;