PEL: Print Extended User Header section to JSON

"Extended User Header": {
    "Section Version":          "1",
    "Sub-section type":         "0",
    "Created by":               "0x4552",
    "Reporting Machine Type":   "OPWR-131",
    "Reporting Serial Number":  "1318ABA",
    "FW Released Ver":          "BE868_007",
    "FW SubSys Version":        "00040905079B0004",
    "Common Ref Time":          "00/00/0000 00:00:00",
    "Symptom Id Len":           "0",
    "Symptom Id":               ""
},

Verified peltool output and all testcases passed.
Signed-off-by: Harisuddin Mohamed Isa <harisuddin@gmail.com>
Change-Id: Id66b9da27d49c89befd157b0e94bbc9defed0d6a
diff --git a/extensions/openpower-pels/extended_user_header.hpp b/extensions/openpower-pels/extended_user_header.hpp
index 422b3f5..b5a447d 100644
--- a/extensions/openpower-pels/extended_user_header.hpp
+++ b/extensions/openpower-pels/extended_user_header.hpp
@@ -155,6 +155,12 @@
         return symptom;
     }
 
+    /**
+     * @brief Get section in JSON.
+     * @return std::optional<std::string> - ExtendedUserHeader section's JSON
+     */
+    std::optional<std::string> getJSON() const override;
+
   private:
     /**
      * @brief Fills in the object from the stream data