Doxygen comments for enum & structure

Added doxygen comments for enums & structures for user & channel
layers.

Unit-test:
verified build.

Change-Id: Ie5af8d6cdd4c04cb396869b7a3dc44f84efedd19
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
diff --git a/user_channel/user_mgmt.hpp b/user_channel/user_mgmt.hpp
index a54486f..0326dca 100644
--- a/user_channel/user_mgmt.hpp
+++ b/user_channel/user_mgmt.hpp
@@ -37,6 +37,9 @@
 
 using DbusUserObjValue = std::map<std::string, DbusUserObjProperties>;
 
+/**
+ * @enum User update events.
+ */
 enum class UserUpdateEvent
 {
     reservedEvent,
@@ -48,6 +51,10 @@
     userStateUpdated
 };
 
+/** @struct UserPrivAccess
+ *
+ *  Structure for user privilege access (refer spec sec 22.22)
+ */
 struct UserPrivAccess
 {
     uint8_t privilege;
@@ -56,6 +63,10 @@
     bool accessCallback;
 };
 
+/** @struct UserInfo
+ *
+ *  Structure for user related information
+ */
 struct UserInfo
 {
     uint8_t userName[ipmiMaxUserName];
@@ -65,6 +76,10 @@
     bool fixedUserName;
 };
 
+/** @struct UsersTbl
+ *
+ *  Structure for array of user related information
+ */
 struct UsersTbl
 {
     //+1 to map with UserId directly. UserId 0 is reserved.