config_parser: Add parser warnings

This makes it possible to determine if the file had formatting issues
and should be rewritten.

Change-Id: I1a1fd683b5733bff1841703dcd7be99688b66c54
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/config_parser.hpp b/src/config_parser.hpp
index 9a30833..abbf25c 100644
--- a/src/config_parser.hpp
+++ b/src/config_parser.hpp
@@ -48,6 +48,14 @@
     const ValueList& getValues(std::string_view section,
                                std::string_view key) const noexcept;
 
+    /** @brief Determine if there were warnings parsing the file
+     *  @return The number of parsing issues in the file
+     */
+    inline const std::vector<std::string>& getWarnings() const noexcept
+    {
+        return warnings;
+    }
+
     /** @brief Set the file name and parse it.
      *  @param[in] filename - Absolute path of the file.
      */
@@ -55,6 +63,7 @@
 
   private:
     SectionMap sections;
+    std::vector<std::string> warnings;
 };
 
 } // namespace config