Add --username option to Clip command. (#3947)

* make Clip accept an attribute name

This allows users to copy arbitrary attributes (e.g. username, notes,
URL) to the clipboard in addition to the password and TOTP values.

* update Clip manpage

* Add findAttributes to CLI utils

* Use case-insensitive search in Show command.

* Use case-insensitive search in Clip command.

Co-authored-by: louib <L0U13@protonmail.com>

src/cli/Utils.cpp

@@ -331,4 +331,21 @@ namespace Utils
         return result;
     }
 
+    QStringList findAttributes(const EntryAttributes& attributes, const QString& name)
+    {
+        QStringList result;
+        if (attributes.hasKey(name)) {
+            result.append(name);
+            return result;
+        }
+
+        for (const QString& key : attributes.keys()) {
+            if (key.compare(name, Qt::CaseSensitivity::CaseInsensitive) == 0) {
+                result.append(key);
+            }
+        }
+
+        return result;
+    }
+
 } // namespace Utils