PEL: Print the JSON formatted UserData

Override the getJSON() function in the  UserData section so it will
support peltool pretty printing when the data has been stored as JSON
(component phosphor-logging, subtype 1 as defined in
user_data_formats.hpp).

It first converts the original JSON string to a nlohmann::json object to
validate it is valid JSON and then uses nlohmann::json's stream <<
operator to convert it into a pretty string.

This also sets up a framework where other UserData parsing functions can
be called from, and it is all only compiled into peltool, and not into
phosphor-log-manager.

The UserData section created out of the OpenBMC event log's
AdditionalData property already makes use of this format.

Here are some example outputs.  Note that the 'Data' key is added by
this code for JSON that isn't already an object (dict) to make it one.

"User Data": {
    "OPERATION": "something",
    "REGISTER_FFDC": "REG1=0x8|REG2=0x9|REG3=0x55",
    "RETURN_VALUE": "-12",
    "TIMEOUT_IN_MSEC": "100",
    "_PID": "993"
},

"User Data": {
    "Data": [
        "OPERATION",
        "REGISTER_FFDC",
        "RETURN_VALUE",
        "TIMEOUT_IN_MSEC",
        "_PID"
    ]
},

"User Data": {
    "Data": "This is a string"
}

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I7b034ac24339b5b019db3b57d8e71cb03559363e
diff --git a/extensions/openpower-pels/pel.hpp b/extensions/openpower-pels/pel.hpp
index 139fda8..ccbef91 100644
--- a/extensions/openpower-pels/pel.hpp
+++ b/extensions/openpower-pels/pel.hpp
@@ -286,6 +286,14 @@
     void checkRulesAndFix();
 
     /**
+     * @brief Returns a map of the section IDs that appear more than once
+     *        in the PEL.  The data value for each entry will be set to 0.
+     *
+     * @return std::map<uint16_t, size_t>
+     */
+    std::map<uint16_t, size_t> getPluralSections() const;
+
+    /**
      * @brief The PEL Private Header section
      */
     std::unique_ptr<PrivateHeader> _ph;
@@ -304,8 +312,11 @@
      * @brief helper function for printing PELs.
      * @param[in] Section& - section object reference
      * @param[in] std::string - PEL string
+     * @param[in|out] pluralSections - Map used to track sections counts for
+     *                                 when there is more than 1.
      */
-    void printSectionInJSON(const Section& section, std::string& buf) const;
+    void printSectionInJSON(const Section& section, std::string& buf,
+                            std::map<uint16_t, size_t>& pluralSections) const;
 };
 
 namespace util