docs: wrote Doxygen comments for all files

refs: #4118

Change-Id: Ib0e7f1926cdabcca5aa401b59b24519412a099f7
diff --git a/src/update/prefix-update-processor.hpp b/src/update/prefix-update-processor.hpp
index 6ee9506..52780e6 100644
--- a/src/update/prefix-update-processor.hpp
+++ b/src/update/prefix-update-processor.hpp
@@ -55,6 +55,18 @@
                         ndn::KeyChain& keyChain,
                         std::shared_ptr<ndn::CertificateCacheTtl> certificateCache,
                         security::CertificateStore& certStore);
+
+  /*! \brief Load the validator's configuration from a section of a
+   * configuration file.
+   * \sa ConfFileProcessor::processConfFile
+   * \sa ConfFileProcessor::processConfSectionSecurity
+   *
+   * Loads the state of the validator for prefix update commands by
+   * reading a section from a configuration file. This function is
+   * expecting the section to be from a Boost property tree object.
+   *
+   * \throws PrefixUpdateProcessor::Error If configuration fails to load successfully
+   */
   void
   loadValidator(ConfigSection section, const std::string& filename);