bmcweb: /s/boost::string_view/std::string_view/g

With boost 1.69, we get the new option, BOOST_BEAST_USE_STD_STRING_VIEW
which allows us to use std::string for all beast interfaces, instead of
boost string_view.  This was originally intended to try to reduce the
binary size, but the comparison shows only a minor improvement.

boost::string_view: 7420780 bytes
std::string_view:   7419948 bytes

832 bytes saved ! ! ! ! !

So instead, we will use the argument that it's more standard and easier
for people to grok.

Tested By:
Pulled down some bmcweb endpoints, and observed no change.  Because the
two objects are essentially drop in replacements for one another, there
should be no change.

Change-Id: I001e8cf2a0124de4792a7154bf246e3c35ef3f97
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
diff --git a/include/sessions.hpp b/include/sessions.hpp
index 510f566..6bc1c99 100644
--- a/include/sessions.hpp
+++ b/include/sessions.hpp
@@ -102,7 +102,7 @@
 {
   public:
     std::shared_ptr<UserSession> generateUserSession(
-        const boost::string_view username,
+        const std::string_view username,
         PersistenceType persistence = PersistenceType::TIMEOUT)
     {
         // TODO(ed) find a secure way to not generate session identifiers if
@@ -148,7 +148,7 @@
     }
 
     std::shared_ptr<UserSession>
-        loginSessionByToken(const boost::string_view token)
+        loginSessionByToken(const std::string_view token)
     {
         applySessionTimeouts();
         auto sessionIt = authTokens.find(std::string(token));
@@ -161,7 +161,7 @@
         return userSession;
     }
 
-    std::shared_ptr<UserSession> getSessionByUid(const boost::string_view uid)
+    std::shared_ptr<UserSession> getSessionByUid(const std::string_view uid)
     {
         applySessionTimeouts();
         // TODO(Ed) this is inefficient